SPECIAL PAPERS IN PALAEONTOLOGY NO. 79

NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS IN A SILURO-DEVONIAN SECTION OF THE TAFILALT, ANTI-ATLAS, MOROCCO

BY BJO¨ RN KRO¨ GER

with 16 plates and 23 text-figures

THE PALAEONTOLOGICAL ASSOCIATION LONDON

March 2008

CONTENTS

Page

Abstract 5 Introduction 5 Terminology 6 Open nomenclature 6 Terminology of higher taxa 6 Morphological terms 6 Diversity Measures 7 The Locality 8 Sedimentary Succession and Stratigraphy 8 1. Temperoceras limestone succession 9 2. Scyphocrinites limestone succession 10 3. Jovellania limestone succession 11 4. Pragian-Zlı´chovian limestone succession 12 5. Early Eifelian limestone succession 14 Interpretation of the Sedimentary Succession 15 Description of depositional cycles 15 Cephalopod Succession 18 Diversity signal 18 Morphological signal 19 Evolutionary signal 21 Systematic Palaeontology 21 Class Cepalopoda Cuvier, 1797 21 Order Discosorida Flower, in Flower and Kummel 1950 21 Family Phragmoceratidae Miller, 1877 21 Genus Pseudendoplectoceras gen. nov. 21 Order Oncocerida Flower, in Flower and Kummel 1950 22 Family Brevicoceratidae Flower, 1945 22 Genus Brevicoceras Flower, 1938 22 Genus Cerovoceras gen. nov. 24 Family Jovellaniidae Foord, 1888 26 Genus Jovellania Bayle, in Bayle and Zeller 1878 26 Genus Bohemojovellania Manda, 2001 27 Family Karoceratidae Teichert, 1939 30 Genus Ankyloceras Zhuravleva, 1974 30 Genus Ventrobalashovia gen. nov 30 Family Nothoceratidae Fischer, 1882 31 Genus Mutoblakeoceras gen. nov. 31 Genus Tafilaltoceras gen. nov. 32 Indet. Nothoceratidae 34 Family Oncoceratidae Hyatt, 1884 34 Genus Orthorizoceras gen. nov. 34 Order Nautilida Agassiz, 1847 35 Family Centroceratidae Hyatt, 1900 35 Genus Centroceras Hyatt, 1884 35 Order Actinocerida Teichert, 1933 35 Family Ormoceratidae Saemann, 1852 35 Genus Ormoceras Stokes, 1840 35 Genus Deiroceras Hyatt, 1884 36 Genus Metarmenoceras Flower, 1940 38 Order Pseudothocerida Barskov, 1963 39 Family Pseudorthoceratidae Flower and Caster, 1935 39 Genus Geidoloceras gen. nov. 39 Genus Neocycloceras Flower and Caster, 1935 40 Genus Probatoceras Zhuravleva, 1978 40 Genus Subdoloceras gen. nov. 41 Genus Subormoceras gen. nov. 43 Family Spyroceratidae Shimizu and Obata. 1935a 46 Genus Spyroceras Hyatt, 1884 46 Genus Cancellspyroceras gen. nov. 50 Genus Diagoceras Flower, 1936 50 Genus Suloceras Manda, 2001 51 Order Lituitida Starobogatov, 1974 52 Family Lamellorthoceratidae Teichert, 1961 52 Genus Arthrophyllum Beyrich, 1850 52 Family Sphooceratidae Flower, 1962 55 Genus Sphooceras Flower, 1962 55 Order Orthoceratida Kuhn, 1940 56 Family Orthoceratidae McCoy, 1844 56 Genus Chebbioceras Klug et al. 2008 56 Genus Infundibuloceras Klug et al. 2008 56 Genus Kopaninoceras Kiselev, 1969 58 Genus Merocycloceras Ristedt, 1968 62 Genus Michelinoceras Foerste, 1932 64 Genus Orthocycloceras Barskov, 1972 65 Genus Pseudospyroceras gen. nov. 68 Genus Theoceras gen. nov. 69 Genus Tibichoanoceras gen. nov. 70 Orthoceratidae gen. et sp. nov. 72 Family Arionoceratidae Dzik, 1984 72 Genus Arionoceras Barskov, 1966 72 Genus Adiagoceras gen. nov. 76 Genus Parakionoceras Foerste, 1928 78 Family Dawsonoceratidae Flower, 1962 80 Genus Anaspyroceras Shimizu and Obata, 1935a 80 Indet. Dawsonoceratidae 81 Family Geisonoceratidae Zhuravleva, 1959 81 Genus Angeisonoceras gen. nov. 81 Genus Temperoceras Barskov, 1960 82 Family Kionoceratidae Hyatt, 1900 85 Genus Kionoceras Hyatt, 1884 85 Family Sichuanoceratidae Zhuravleva 1978 86 Genus Sichuanoceras Chang, 1962 88 Family Sphaerorthoceratidae Ristedt, 1968 89 Genus Sphaerorthoceras Ristedt, 1968 89 Genus Akrosphaerorthoceras Ristedt, 1968 89 Genus Hemicosmorthoceras Ristedt, 1968 90 Genus Parasphaerorthoceras Ristedt, 1968 91 Genus Plagiostomoceras Teichert and Glenister, 1952 92 Order Bactritida Shimansky, 1951 95 Family Bactritidae Hyatt, 1884 95 Genus Bactrites Sandberger, 1843 95 Genus Devonobactrites Shimansky, 1972 95 Genus Lobobactrites Schindewolf, 1932 97 List of New Combinations 97 Conclusions 98 Acknowledgements 100 References 100 Appendix 107 PALA 764 Dispatch: 28.1.08 Journal: PALA CE: Blackwell Journal Name Manuscript No. B Author Received: No. of pages: 106 PE: Raymond [Special Papers in Palaeontology, 79, 2008, pp. 5–110]

1 Abstract: The non-ammonoid cephalopod fauna of the deposition of key horizons is estimated. Cephalopods occur 2 Siluro-Devonian section of Filon Douze, in the southern mainly in three different facies types: (1) massive lime- 3 Tafilalt, Morocco is described. The section spans a sedi- stones, silty shales and marls with a bivalve-orthocerid 4 mentary succession of predominantly argillites with interca- association, reflecting (par-)autochthonous conditions in a 5 lated cephalopod limestones of Ludlow–Eifelian age with a distal environment below storm wave base; (2) proximal 6 thickness of c. 450 m. More than 2000 cephalopods were tempestites with a bivalve-orthocerid association, reflecting 7 collected bed by bed and comprise 52 genera (17 new) and (par-)autochthonous conditions in a distal environment 8 86 species (39 new). Only one discosorid occurs, the new above storm wave base; and (3) marls and nodular lime- 9 taxon Pseudendoplectoceras lahcani. The oncocerids are stones containing orthocones and a diverse benthos reflect- 10 highly endemic, since out of nine recorded genera five are ing a well-oxygenated environment below storm wave base. 11 new: Cerovoceras, Mutoblakeoceras, Orthorizoceras, Tafilalto- The bivalve-orthocerid association is exclusively pre-Pra- 12 ceras and Ventrobalashovia. Only one of 13 oncocerid gian. The bivalve-orthocerid storm beds abruptly disappear 13 species is known from elsewhere and nine are new: at the top of the Lochkovian. The Pragian, Emsian and 14 Bohemojovellania adraei, B. obliquum, Brevicoceras magnum, Eifelian sediments invariably contain cephalopods together 15 Cerovoceras brevidomus, C. fatimi, Jovellania cheirae, Mut- with a highly diverse benthos. A significant increase in 16 oblakeoceras inconstans, Tafilaltoceras adgoi and Ventrobala- cephalopod richness and taxonomic distinctness occurs in 17 shovia zhuravlevai. Three actinocerids occur, two of which, the uppermost Lochkovian tempestites. The Lochko- 18 Metarmenoceras fatimae and Deiroceras hollardi, are new. vian ⁄ Pragian boundary also marks a profound change in 19 Within the Pseudorthoceratida the new taxa Cancellspyroc- the morphological composition of the cephalopod associa- 20 eras, Geidoloceras ouaoufilalense, Subdoloceras atrouzense, S. tion. In the uppermost Lochkovian several cephalopod taxa, 21 tafilaltense, and S. engeseri, Subormoceras erfoudense and S. which were adapted to the low energy needs that domi- 22 rissaniense are erected. The pseudorthoceratid species Neo- nated during the late Silurian and earliest Devonian, have 23 cycloceras termierorum, Spyroceras cyrtopatronus, S. latepatr- their last occurrence. In post-Lochkovian strata cephalopod 24 onus and Sulcoceras longipulchrum are also erected. New morphotypes that were adapted to energy-intensive buoy- 25 genera and species of the Orthocerida are Adiagoceras taou- ancy regulation dominate. Finally, in late Pragian and 26 zense, Angeisonoceras reteornatum, Chebbioceras erfoudense, Zlı´chovian deposits, bactritoids sensu stricto, ammonoids, 27 Infundibuloceras brevimira, I. longicameratum, I. mohamadi, coiled nautiloids and several pseudorthocerids have their 28 Pseudospyroceras reticulatum, Theoceras felondouzense and first occurrence. These groups dominated in the late Palae- 29 Tibichoanoceras tibichoanum. Additionally, the orthoceratid ozoic. Therefore, the changes at the Lochkovian ⁄ Pragian 30 species Hemicosmorthoceras aichae, Orthocycloceras tafilal- boundary resulting in better conditions for life on the sea- 31 tense, Plagiostomoceras lategruenwaldti, P. reticulatum, Sic- floor can be interpreted as a precondition that led to the 32 huanoceras zizense and Temperoceras aequinudum, and the landmark evolutionary innovations in the Zlı´chovian. 33 bactritoid species Devonobactrites emsiense are erected, and 34 21 species are transferred to different genera. The strati- Key words: Cephalopoda, bactritoid origin, cephalopod 35 graphical section is described in detail and the depth of limestones, Silurian, Devonian, Morocco 36 37 38 39 40 In the early Middle Devonian (Zlı´chovian) the ammo- and Klug 2003). However, the ammonoids did not enter 41 noids appeared and quickly evolved to be the dominant an empty cephalopod universe. The seas of the Early 42 shelled cephalopods until the end of the Cretaceous Per- Devonian were inhabited by a multitude of cephalopods 43 iod. The ammonoid origin and initial radiation, including prior to their appearance and the incipient ammonoid 44 its timing and morphological pathways, are comparably faunas had to share their ecosystem with several close rel- 45 well known (Erben 1960, 1964; Bogoslovsky 1969; Korn atives. Bactritoids and Orthocerida are the closest relatives 46 47 48 49 50 51 BJO¨ RN KRO¨ GER 52 Universite´ des Sciences et Technologies de Lille 1, Sciences de la Terre, Laboratoire de Pale´ontologie (LP3), UMR 8014 et FR 1818 du CNRS, baˆtiment SN5, 59655 53 Villeneuve d’Ascq Cedex, France; formerly Museum fu¨r naturkunde der Humboldt Universita¨t zu Berlin, Invalidenstraße 43, D-10115 Berlin, Germany; 54 e-mail [email protected]

The Palaeontological Association doi: 10.1111/j.1475-4983.2008.00764.x 5 6 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 of ammonoids, since they share a small spherical embry- throughout Morocco and North Africa and of the com- 2 onic shell and a very narrow siphuncle that lacks deposits. monality of many faunal elements across the Rheic 3 2Finds of orthocerid radulae (Mehl 1984; Gabbott 1999) Ocean from Bohemia to the Carnic Alps, Armorica, 4 suggest not only similar feeding habits but also close phy- Sardinia and Morocco (Gnoli 2003). Specific orthocerid 5 logenetic relationships between ammonoids and ortho- beds can be traced in North Africa from Mali to Algeria 6 cerids. (Krˇı´zˇ 1998; Gnoli 2003). This detailed report of the 7 The evolution of these close relatives just before, dur- stratigraphical occurrences at this single locality is 8 ing, and after the appearance of ammonoids has never intended to serve as a reference for future investigations 9 been investigated. A study of the literature reveals that in other regions of the world. 10 no information is available on the diversity and com- 11 monality of bactritoids in the Late Silurian–Middle 12 Devonian. It is not even clear when the direct ancestors TERMINOLOGY 13 of the ammonoids appeared. Ristedt (1981) described a 14 single species of a Ludlow bactritoid from Bohemia, but Open nomenclature. The open nomenclature follows the 15 questioned a direct ancestry of the Devonian bactritoids recommendations of Bengtson (1988). Thus, ‘?’ following 16 from that Silurian specimen. Beside this species, no a generic or specific name denotes uncertainty of the 17 unquestionable pre-Zlı´chovian bactritoids have been determination because of poor preservation or poor 18 reported. A similar situation exists in knowledge of the material; quotation marks ‘…’ indicate that the genus or 19 evolution of post-Lochkovian orthocerids. Orthocerids species is regarded as obsolete in the current context; ‘cf.’ 20 are the dominant elements in the cephalopod limestone indicates that the specific identification is provisional and 21 biofacies (Krˇı´zˇ and Ferretti 1995; Krˇı´zˇ 1998) of peri- further material is needed in order to establish a new 22 Gondwanan low latitudes. The orthocerids of this facies species or to confirm the present assignment. 23 have been intensively investigated (Babin 1966; Ristedt 24 1968; Serpagli and Gnoli 1977; Gnoli 1982; Holland Higher taxa. I use a variety of endings to distinguish 25 et al. 1994; Histon 1999; see also references in Gnoli related higher taxa: nautilids, nautilidans and nautiloi- 26 2003). However, these orthocerid-dominated limestones dans; and bactritids, bactritidans and bactrioids. The end- 27 disappear towards the top of the Lochkovian (Krˇı´zˇ 1998, ings ‘-ids’ indicate the specific family, ‘-idans’ a subgroup 28 1999; Gnoli 2003) and the orthocerid-bearing limestones of the specific order that does not coincide with a partic- 29 of the post-Lochkovian have been rarely investigated ular family, and ‘-oids’ a group that in some aspects is 30 with a focus on orthocerids. Although post-Lochkovian similar to the specific family. 31 Devonian orthocerids have been described in several 32 papers (e.g. Foerste 1926, 1927, 1929; Flower 1936, 1939, Morphological terms. The conch is divided into a left and 33 1949; Balashov and Kiselev 1968; Zhuravleva 1978; Gnoli a right side from a perspective viewed in the direction of 34 1982), the stratigraphical control of the occurrences of growth along the dorsoventral axis. The cross-section of 35 the cephalopods described is often poor, making detailed the conch is compressed when it is higher than wide, and 36 comparisons with ammonoid occurrences difficult. depressed, when wider than high. The shell surface is 37 Therefore, from the study of the literature it is impossi- ornamented by striae when two successive grooves form a 38 ble to evaluate how non-ammonoid cephalopods, specifi- band in between; by lirae when raised lines occur; by 39 cally the orthocerids, developed during the initial ridges when the conch is locally thickened forming acute 40 ammonoid radiation in the earliest Emsian. The current or rounded waves (Text-fig. 1). 41 work is intended to contribute to the knowledge of The shape of the septal neck is defined by the angle 42 stratigraphical occurrences of non-ammonoid cephalo- of inflection relative to the direction of the septal sur- 43 pods in this critical time interval. face, which is usually approximately perpendicular to 44 During two field trips in 2003 and 2005, I collected the growth axis. The septal necks are achoanitic when 45 more than 2000 cephalopod specimens, bed by bed, very short or lacking and too short to detect the angle 46 from a section in the Tafilalt of south-east Morocco of inflection; loxochaonitic when the tips of the necks 47 spanning the Ludfordian–early Eifelian. For the first point at an angle of less than 90 degrees; orthochoanitic 48 time, non-ammonoid cephalopod occurrences were when the angle is nearly 90 degrees; suborthochoanitic 49 recorded against a precisely controlled stratigraphical when it is 90–180 degrees; and cyrtochoanitic when it is 50 record in post-Lochkovian Devonian sediments. more than 180 degrees. The septal necks are recumbent 51 Although the cephalopods were collected only at a single when the brim touches the adapical surface of the 52 locality, it is assumed that the occurrences represent related septum. 53 some general pattern. I draw this conclusion from the The siphuncle is subcentral when it is removed from 54 widespread geographical occurrence of orthocerid beds the growth axis by a distance less than its own diameter, 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 7

1 A the Deiroceras limestones). The number of specimens col- 2 lected reflects their accessibility rather than their real 3 B abundance. Collecting in clay and in siltstones, where the 4 fossils washed out and accumulated on the bed surface, 5 C was easier than collecting from limestones that in some 6 cases only cropped out with surfaces perpendicular to the 7 D bedding planes. Moreover, I did not collect every single 8 specimen in limestones but only when easily accessible 9 E and with a focus on reaching the greatest richness during 10 collecting. In contrast, I collected every specimen in the TEXT-FIG. 1. Illustrations of types of surface ornamentation 11 in median section. A, striae. B–C, lirae. D, ridges. E, clay, siltstones, and marls regardless of their preservation 12 undulations. Not to scale. and type. The diversity estimation is further complicated 13 by different preservation in specific beds. The fauna of 14 bed OP-M is recorded only by internal moulds of the 15 eccentric when it is removed from the growth axis by a conchs, that of bed EF by limonitic steinkerns, and other 16 distance more than its own diameter, and marginal, when beds preserved a fauna with more or less well-preserved 17 it touches the shell wall. The cameral deposits are hypo- but recrystallized conchs. These differences in preservation 18 septal when covering the adapical septal surfaces; episeptal, and collecting practice were minimized by sample stan- 19 when covering the adoral septal surfaces; and epichoanitic dardization, and by excluding some beds from diversity 20 when covering the septal necks (Text-fig. 2). The endosip- estimation. Only beds OP-M, PK, OJ-I, KMO-I–KMO-IV 21 huncular deposits are annulate when arranged symmetri- and EF were considered for diversity estimation. I col- 22 cally, or nearly so, around the septal perforation, and lected a large number of specimens from these beds; every 23 parietal when annuli are either adorally or adapically fragment, regardless of preservation or type. 24 elongated. Species richness was calculated using the method of 25 Chao (1984) following Chazdon et al. (1998) (Table 1). 26 The advantage of this method is that it is not based on 27 DIVERSITY MEASURES the parameters of a species abundance model that has 28 previously been fitted to the data. Magurran (2004) dem- 29 The number of specimens collected from each bed differs onstrated that the Chao estimators are among the most 30 greatly (see Appendix), since from some beds several hun- robust diversity measures developed in recent years. The 31 dreds of specimens were recovered (the maximum was absolute number of species in a sample is estimated as 32 more than 550 specimens from bed EF), whereas others S S F 2 F 33 yielded only a few specimens (only five specimens from chao1¼ obsþð 1 =2 2Þ 34 35 where Sobs is the number of species in the sample, F1 is 36 the number of observed species represented by a single 37 specimen, and F2 is the number of species represented by 38 two specimens. For the calculation of Schao1 I used Esti- 39 mateS software (Colwell 2005). Nevertheless, the richness 40 estimate is dependent on sampling intensity; it is gener- 41 ally underestimated in samples unless a very large sam- 42 pling size is used. Magurran (2004) proposed a simple 43 check for the accuracy of the estimations. When the total 44 sample is subdivided into two subsamples at random and 45 an estimate of the richness of the subsamples is obtained 46 separately, the results should be consistent with those 47 obtained from the total sample. I checked this for the 48 samples of the Filon Douze section (Text-fig. 3; Table 2). 49 cameral deposits 1 mm The results show that a sufficient sample size is reached only in beds OP-M, PK and EF, the remaining samples 50 TEXT-FIG. 2. Epichoanitic deposits, camera lucida drawing of 51 median section of Arthrophyllum vermiculare; MB.C. 9648; consistently under-evaluate the richness of the total sam- 52 Pragian, Filon Douze section, Tafilalt, Morocco. Note the ple. However, Text-figure 3 also shows that even in the 53 coverage of entire septal necks by cameral deposits. Ventral is to case under-estimating total richness, the general pattern 54 the right. of the diversity trend is not altered. 8 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 TABLE 1. Diversity measures of selected beds in the Filon Douze section. Abbreviations: Sobs (Mao Tao), number of species expected ⁄ 2 given the total occurrences after Colwell et al. (2004); Sobs 95% confidence lower boundary upper boundary, lower and upper bound- ⁄ 3 ary of 95% confidence level of Sobs (Mao Tao); SChao 1, Chao 1 richness estimator after Chao (1984); SChao 1 95% confidence lower 4 upper boundary, lower and upper boundary of 95% confidence level after Chao (1987). All values are calculated with EstimateS (Colwell 2005). 5 6 OP PK 0J-I KMO-I KMO-II KMO-III EF 7 8 Occurrences (total) 441 103 302 84 129 40 560 S (Mao Tao) 13 3 17 10 13 13 7 9 obs S 95% confidence lower b. 6 0 10 5 6 6 2 10 obs Sobs 95% confidence upper b. 20 6 24 16 20 51 12 11 SChao 1 21 4 18 18 17 25 7 12 SChao 1 95% confidence lower b. 14 3 17 11 14 15 7 13 SChao 1 95% confidence upper b. 78 11 27 74 42 81 7 14 Shannon evenness 1.26 0.15 1.33 1.55 1.71 2.03 0.57 15 Simpson evenness 2.55 1.06 2.45 3.49 3.8 5.77 1.32 16 17 18 19 total random choice a random choice b weighted the path length assigned to each level of the tax- 20 95% confidence interval of total sample onomic hierarchy as 1. Thus, each step up in the hierar- chy of a shared taxonomic level (from species to genus, 21 55 22 family and order) increments have the value 1. 23 Additionally I calculated the Shannon index H’ and the 24 45 Simpson index D as evenness measures using EstimateS 25 software (Colwell 2005) in order to evaluate the hetero- 26 35 geneity of the samples. 27 28 29 25 THE LOCALITY 30

31 Chao 1 species richness 15 The succession investigated is a natural outcrop across a 32 dry valley in the Tafilalt, Anti-Atlas, a region in south- 33 eastern Morocco south of the city of Errachidia, between 5 34 Erfoud and the military post Taouz (Text-fig. 4). The sec- 35 OP-MPK OJ-I KMO-I KMO-II KMO-III EF tion is located c. 10 km north-east of Taouz, spanning 36 TEXT-FIG. 3. Chao 1 richness of total samples and two the entire unnamed valley south of the ridges of the 37 random subsamples. Bars indicate 95 per cent confidence levels Jebel Ouaoufilal at the section 30º56.592 ⁄ 004°03.059 – 38 of the total sample. Calculated richness in random subsamples is 30°57.095 ⁄ 004°02.290 slightly south of the abandoned 39 considerably lower than in total sample from bed KMO-I–III, lead mine of Filon Douze. The section of Hollard (1977, 40 but the general diversity pattern with low values in beds PK and fig. 4) represents the same locality, but was probably mea- 41 EF is preserved; for data, see Tables 2–3. sured several hundred metres to the north of Filon Douze. The sections at Jebel Ouaoufilal of Klug (2001, 42 In addition to the Chao richness estimator, I calculated 2002), and Klug et al. (in press) are nearly identical to 43 the taxonomic distinctness following Clarke and Warwick the Early and Middle Devonian intervals of the section 44 (1998, 1999) (for data, see Table 3). Taxonomic distinct- considered herein. 45 ness provides a measure of the relatedness of the species 46 in a sample. It can be interpreted as an approximation of 47 disparity in cases where few or no homoeomorphic taxa 48 occur, which is the case in the Filon Douze section. The SEDIMENTARY SUCCESSION AND 49 taxonomic distinctness index D+ is calculated as: STRATIGRAPHY 50 þ À1 51 D ¼ðRRi

1 TABLE 2. Diversity measures of two random subsamples of the total occurrences in the Filon Douze section given in Table 1. Note 2 the lower calculated richness values in all beds, exclusive of EF. However, the general pattern with low richness values in bed PK and 3 EF is preserved in the random samples. Abbreviations as in Table 1. 4 OP PK 0J-I KMO-I KMO-II KMO-III EF 5 6 Random Sample A 7 Occurrences (total) 206 62 79 68 36 17 31 8 Chao 1 9 2 12 18 13 13 7 Chao 1 95% confidence lower b. 9 2 10 10 10 10 7 9 Chao 1 95% confidence upper b. 13 2 29 60 38 35 7 10 Random Sample B 11 Occurrences 147 41 220 29 83 21 251 12 Chao 1 11 4 18 12 13 10 7 13 Chao 1 95% confidence lower b. 5 3 15 9 11 8 7 14 Chao 1 95% confidence upper b. 17 16 40 28 25 27 7 15 16 17 TABLE 3. Taxonomic distinctness of selected beds in the Filon (pers. comm. 2006). The unit was termed ‘Orthoceras 18 Douze section calculated after Clarke and Warwick (1998, 1999). Limestone’ by Hollard (1977, p. 182). Taxonomic distinctness provides a measure of the relatedness of 19 the taxa in a sample. Note the increased values in beds of the 20 Thickness. Approximately 5 m. Jovellania Limestones and above. 21 22 Bed Taxonomic distinctness (+) Description. The base of the unit consists of a massive 2- 23 m-thick, dark, biodetrital pelagic mudstone (bed OP). At OP 2.7 24 the base of the bed large load casts occur. There are sev- OSP-I+II 2.6 25 PK 2.7 eral horizons with Temperoceras, which are c. 20–50 mm 26 OJ-I+II 3.4 in cross-section. The orthocones are predominantly orien- 27 KMO-I 3.7 tated in an east ⁄ west direction (80 ⁄ 260 degrees) and the 28 KMO-II 3.5 apices are directed towards the west. 29 KMO-III 3.4 Above OP a succession of dark mudstones to wacke- 30 EF 3.3 stones and thin argillites with a thinning-up tendency in 31 KMO-IV 3.8 the limestones occurs. Frequently orthocones occur which 32 Erbenoceras Limestone 3.9 are smaller than in the underlying massive limestone 33 jugleri Limestone 3.5 (0.1–0.3 m in cross-section); the bivalve Cardiola is com- 34 mon. Towards the top of the bed the orthocones and biv- 35 alves occur less frequently, and finally are almost absent. 36 vian beds of the southern Tafilalt are comparatively The argillaceous limestone changes to a silty claystone 37 poorly known: only short descriptions were provided by (bed OP-M) towards the top. This bed is about 1 m thick 38 Hollard (1977). A detailed stratigraphical analysis of the and contains masses of small orthocones (cross-section c. 39 early Emsian–middle Eifelian succession of sections of the 10 mm), predominantly Arionoceras and Kopaninoceras. 40 southern Tafilalt was provided by Klug (2001, 2002). Within the claystone large dark concretions (floatstone) 41 Parts of the Lochkovian succession of the northern Tafil- occur (with horizontal diameters up to 0.5 m and a 42 alt were described by Alberti (1969), Belka et al. (1999) thickness up to 0.3 m); these contain a different fauna of 43 and Bultynck and Walliser (2000). Several key horizons orthocones with predominantly Kopaninoceras and Plagio- 44 can be distinguished at the Filon Douze section. stomoceras. The orthocones in the concretions are poorly 45 The sedimentary succession is divided here into five sorted and small fragments (cross-section <2 mm) occur 46 portions, indicated from oldest to youngest by 1–5 below. beneath large fragments (cross-section >100 mm). 47 Remarkably, the large orthocones are often vertically 48 orientated. 49 1. Temperoceras limestone succession (Text-fig. 5) Above the marl a reddish–brownish, 0.5-m-thick, sand- 50 stone occurs that possesses scour and fill structures and 51 Biostratigraphy. Polygnathoides siluricus conodont Bioz- an erosional surface at the top. Occasional small, indeter- 52 one, early Ludfordian after Hollard (1977) and Brachert minable orthocones occur in this bed. 53 et al. (1992); but Ozarkodina snajdri-Ozarkodina crispa Above the sandstone a thin (0.02–0.05 m) biodetrital 54 conodont Biozone, late Ludfordian after Stefan Lubeseder limestone occurs that contains masses of pelmatozoan 10 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 anean 4‘‘ 00 200 km Mediterr 2 Sea n Cretaceous - Tertiary s Devonian 3 ea Rif a c tl Pre-Devonian O A 4 Rabat 31‘‘ 50 COLOUR c le i d 5 id ERFOUD ant M tl Meseta 6 A 7 Atlas High 8 9 RISSANI 10 Agadir as tl E 11 -A C ti gr n h A e 12 b ib 13 Meso-Cenozoic Palaeozoic 14 Precambrian 31‘‘ 00 A 15 Filon Douze 16 Taouz 17 20 km B

18 TEXT-FIG. 4. A, geological map of north-east Africa; rectangle shows area of B, which is a geological map of the Tafilalt, Anti-Atlas, 19 Morocco, and shows the location of the Filon Douze section in the south. 20 21 22 23 Temperoceras limestone succession The limestone is covered by a silty sandstone more 24 than 100 m thick whose arenitic content decreases quickly 25 sandstone within the basal few metres. 26 limestone 27 marl/claystone/silty-marl 28 2. Scyphocrinites limestone succession (Text-fig. 6) 29 ⁄ 30 OP-M Biostratigraphy. Spathagnathodus steinhornensis Ligonodi- 31 na detorta conodont Biozone–Icriodus postwoschmidti ⁄ wo- 32 schmidti conodont Biozone, latest Prˇı´dolian–earliest? 33 Lochkovian after Haude and Walliser (1998). Because the 34 postwoschmidti ⁄ woschmidti conodont Biozone spans an condont Zone 35 interval from latest Silurian to earliest Devonian and 36 because no new graptolite data are available, the precise 37 position of the Siluro-Devonian boundary is not known 38 at Filon Douze. Hollard (1977) reported Monograptus ex 39 gr. lochkovensis from his bed TM 714, which is considered 40 similar to bed S-II of this investigation. This graptolite is 41 indicative of the Ozarkodina remscheidensis interval–L. de- 42 torta conodont Biozone of the latest Silurian. Belka et al. (1999) reported a conodont fauna within the Scyphocri- 43 Polygnathoides siluricus OP 44 nites limestone succession from eastern Tafilalt that is

45 m indicative of the Early Devonian Ozarkodina eurekaensis 46 1 conodont Biozone. However, it is not clear which horizon 47 in the Scyphocrinites limestone succession of the Filon TEXT-FIG. 5. Section of the Temperoceras limestone Douze section the sample of Belka et al. represents. On 48 succession, Ludfordian (Ludlow), Filon Douze, Tafilalt. This 49 section is rich in orthoceridans (mainly Arionoceras, the basis of this evidence, I consider the boundary ques- 50 Kopaninoceras, and Temperoceras) and bivalves. tionably to be at the base of the crinoidal calcarenite (bed 51 C) that succeeds the uppermost Scyphocrinites horizon 52 debris, bivalves and small orthocones (mainly Arionoceras, (bed S-II) at Filon Douze. 53 cross-section <10 mm); it is terminated by a limonite- 54 impregnated, irregular omission surface. Thickness. Approximately 7 m. 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 11

1 Scyphocrinites limestone succession small orthocones (cross-section c. 10–20 mm) and bra- 2 chiopod shell hash. Several of the orthocone fragments 3 are vertically orientated. Pelmatozoan ossicals are rare in 4 OSP-IIa. 5 A black biomicritic floatstone (OSP-IIb), which con- 6 C tains common pelmatozoan debris and masses of ortho- Devonian 7 cones, is intercalated within clay- to siltstones c. 0.5 m 8 loboliths S-II above OSP-IIa. The diversity of orthocones is exception- 9 ally high. Kopaninoceras, Orthocycloceras and Hemicosmor- 10 thoceras are common, and a characteristic element is 11 OSP-IIb Parakionoceras originale; they are randomly orientated. 12 OSP-IIa The bed consists of a 0.25-m-thick conspicuous limestone 13 S-I at the top and a 0.25-m thickening-upward succession of 14 argillitic limestones at the base. 15 A 1-m-thick claystone occurs above OSP-IIb. Approxi- 16 mately 0.7 m from the base of this claystone there is a 17 horizon that contains masses of articulated floats of

18 Silurian Scyphocrinites (‘loboliths’). The claystone is terminated by 19 an encrinitic packstone (S-II) c. 0.5 m thick that contains 20 commonly articulated parts of Scyphocrinites. 21 Above S-II is a massive crinoidal calcarenite 0.45 m 22 thick (bed C). The top of bed C is a conspicuous, partly m OSP-I 23 1 limonitically impregnated, omission horizon. No cephalo- 24 pods occur in the lobolith horizon and in beds S-II and 25 C. 26 bivalves dacryoconarids The Scyphocrinites limestone succession is overlain by a 27 ginger to pale grey succession of clays and siltstones more 28 crinoids orthocone cephalopods than 100 m thick. Approximately 40 m above, a horizon 29 with common phosphatic nodules occurs (bed PK). These trilobites 30 ammonoids nodules contain masses of Plagiostomoceras culter and 31 occasionally Hemicosmorthoceras semimbricatum. rugose corals 32 gastropods 33 TEXT-FIG. 6. Section of the Scyphocrinites limestone 34 succession, Prˇı´dolı´an–Lochkovian, Filon Douze, Tafilalt. 3. Jovellania limestone succession (Text-fig. 7) 35 Orthoceridans (mainly Kopaninoceras and Plagiostomoceras) are 36 concentrated in beds OSP-I and OSP-II. Biostratigraphy. Pedavis pesavis conodont Biozone, latest 37 Lochkovian. The Jovellania limestone succession is not to 38 Description. The lowermost part of the succession (OSP- be confused with the ‘Jovellania’ Limestone’, an informal 39 I) is a 0.5-m-thick succession of black biomicritic float- term of H. Hollard that was adopted by Bultynck and 40 stone that is intercalated with thin argillaceous horizons, Walliser (2000). The latter refers to a limestone that can be 41 which contain masses of orthocones (Kopaninoceras, Pla- correlated with the Deiroceras Limestone of my investiga- 42 giostomoceras) with cross-sections between 10–20 mm but tion. In the Deiroceras Limestone of Filon Douze not a sin- 43 without Scyphocrinites. They are strongly orientated in a gle Jovellania was found. In contrast, Jovellania and other 44 north-east ⁄ south-west direction (50 ⁄ 230 degrees) with oncocerids constitute a common element in the limestone 45 apices directed towards the south-west. At the base of the succession described below. The Jovellania limestone suc- 46 succession two individual 0.15-m-thick limestone beds are cession is considered to represent the pesavis Bioevent 47 distinguishable. (Lochkov ⁄ Prag Event sensu Scho¨nlaub 1996, and Chlupa´cˇ 48 Silt ⁄ claystones occur until c. 3 m above OSP-I where a and Kukal 1996), which is linked with a major worldwide 49 0.15-m-thick encrinitic packstone is intercalated (S-I). regression (Talent et al. 1993; Hladı´kova´ et al.1997). Belka 50 Pelmatozoan debris is the main bioclastic component of et al. (1999) and Bultynck and Walliser (2000) correlated 51 this dark limestone; orthocones are very rare. the base of the Pragian in the eastern Tafilalt with a con- 52 Approximately 0.2 m above S-I a 0.05-m-thick grey bi- spicuous colour change in the siltstones below the Pragian 53 omicritic and partly biosparitic pack- to floatstone occurs limestones, which occurs at the Filon Douze section just 54 (OSP-IIa) that contains masses of randomly orientated above the Jovellania limestone horizon. The Jovellania lime- 12 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 stone succession corresponds to bed TM 212 of Hollard Above OJ-I a dark grey claystone follows that contains 2 (1977), and the occurrence of the tentaculite Homoctenow- carbonate nodules up to 0.5 m wide which commonly 3 akia bohemica in it, and in bed BS, are indicative of the late contain orthocones. The claystones containing the nod- 4 Lochkovian age of the succession. ules are topped by black bituminous argillaceous silt- to 5 sandstone of 0.3 m (BS). Towards the top of BS the aren- 6 Thickness. Approximately 7 m. itic content decreases markedly and the bed appears as 7 finely laminated, dark brownish, bituminous shale. It 8 Description. The lowermost bed, OJ-I, is a dark biomicrit- commonly contains small fragments (cross-section 9 ic silty floatstone <0.1 m thick that contains masses of <10 mm) of orthocones (Arionoceras and diverse sphaer- 10 poorly orientated orthocones of mainly Adiagoceras gen. orthocerids) and dacryonocarids (Homoctenowakia bohe- 11 nov. and Hemicosmorthoceras. Large bivalves (Panenka) mica), which are the only macrofaunal components. The 12 occur at the top of the bed. The bed is characterized by shales successively change towards dark grey clay–silt- 13 the occurrence of scour and fill structures c. 0.15 m thick stones. 14 with a diameter of <0.5 m. These structures contain a Approximately 3 m above BS a massive dark biomicritic 15 floatstone with masses of poorly orientated orthocones. floatstone 0.3 m thick occurs, which contains masses of 16 Beneath the small orthocerids, large Sichoanoceras and very poorly sorted and orientated orthocones (OJ-II) in 17 Temperoceras, and oncocerids such as Jovellania and Bohe- which dacryoconarids (Homoctenowakia bohemica and 18 mojovellania are common. Paranowakia intermedia) are common. This bed is sorted 19 with large components at the base and smaller components 20 concentrated at the top. The largest fragments of ortho- 21 Jovellania limestone succession cones are of Temperoceras with a cross-section diameter of 22 more than 150 mm; the most frequent is Arthrophyllum. In 23 the top 0.05 m of the bed masses of small bivalves (Pteri- 24 nea) occur. This semi-infaunal bivalve is indicative of

25 Zone (Pragian) poorly oxygenated bottom conditions similar to those indi- 26 cated by the closely related pectinids (Krˇı´zˇ 1999). 27 Directly above OJ-II there is a conspicuous purple to 28 sulcatus pinkish claystone that contains masses of pelmatozoan 29 DS debris and small bivalves (Cheiopteria). Approximately 30 0.2 m above OJ-II a horizon is intercalated in this clay- CK 31 stone with ochre-coloured limestone nodules that contain 32 OJ-II masses of small (cross-section 3 mm) Cheiopteria and 33 commonly Hemicosmorthoceras (bed CK). 34 The top of the Jovellania limestone succession is a 35 sandstone 0.5 m thick with a 0.1-m-thick arenitic marl 36 intercalation in its middle part (DS). This sandstone is 37 overlain by a yellowish, greenish to pale grey clay silt- 38 stone, which contains a sand fraction that successively 39 decreases above its base. Zone (Lochkovian) 40 BS 41

42 pesavis 4. Pragian–Zlı´chovian limestone succession (Text-fig. 8) 43 44 Biostratigraphy. Eognathodus sulcatus conodont Biozone, 45 earliest Pragian–Polygnathus laticostatus-inversus conodont 46 Biozone, latest Zlı´chovian, early Emsian (after Klug 2002). 47 The ammonoid fauna of the upper part of the succession OJ-I 48 m was described in detail by Klug (2002). The limonitic fau- 49 1 nas of the claystones below the Erbenoceras and Deiroceras

50 TEXT-FIG. 7. Section of the Jovellania limestone succession limestones are the subject of a monograph by Klug et al. 51 (base of OJ-I to top of DS), Lochkovian, Filon Douze, Tafilalt. (2008). However, despite the good overall fossil content, 52 This section is rich in orthoceridans (mainly Adiagoceras gen. pinpointing the Pragian ⁄ Zlı´chovian and the Zlı´cho- 53 nov. and Hemicosmorthoceras) and bivalves; jovellanids are vian ⁄ Dalejan boundaries at Filon Douze is not possible 54 common; for explanation of symbols, see Text-figure 6. because index fossils that are used in Bohemia (see Chlupa´c 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 13

1 1999) are rare around the potential boundary intervals. The Pragian – Zlichovian limestones 2 earliest trilobites indicative of Pragian age are found at the 3 top of bed KMO-I (Crotalocephalina gibba, Reedops sp.). 4 Erbenoceras Limestone 5 Thickness. Approximately 60 m. 6 KMO-IV

7 Description. Directly above the uppermost sandstone Zlichovian Deiroceras Limestone 8 bed (DS) of the Jovellania limestone succession a yel- EF 9 lowish siltstone 2.5 m thick forms the basal Pragian. 10 Within this siltstone (c. 0.05 m thick) layers of nodular 11 limestones are intercalated that increase in thickness 12 and carbonate content towards the top. The top of the 13 layer is composed of a 0.2-m-thick, massive yellowish 14 biodetrital succession of limestones with a high content 15 of pelmatozoan debris, and fragments of trilobites 16 (Crotalocephalina gibba, Reedops sp.; bed KMO-I). The 17 dominant orthocones are Temperoceras, Arthrophyllum 18 and Spyroceras. 19 Above these limestones, a 13-m-thick succession of 20 platy greenish claystones follows; this is terminated by a 21 massive greenish–pale grey biodetrital limestone 0.1 m 22 thick, which contains pelmatozoan debris but otherwise is 23 poor in macrofossils except for solitary corals (K4). K2 24 Limestone K4 is covered by a 5-m-thick succession of Pragian 25 platy greenish claystones (KMO-II) intercalated with nod- 26 ular pelmatozoan biodetrital limestone layers. These lime- KMO-III 27 stone layers are concentrated in the middle interval of 28 KMO-II and contain a rich fauna of orthocones (predom- K3 29 inantly Arthrophyllum, Temperoceras and pseudorthocer- 30 ids). Trilobites, gastropods and solitary corals constitute a KMO-II 31 rich benthos. K4 32 Limestone K3 consists of two distinct pelmatozoan bio- 33 detrital wackestone to grainstone beds; the lower bed is 34 0.1 m and the upper bed 0.3 m thick; in between is a 35 marl 0.2 m thick that contains limonitized pyrite crystals 36 but lacks a macrofauna. The lower limestone bed of K3 is 37 nodular and contains a high percentage of sand and bio- KMO-I 38 detritus; the bivalve Panenka occurs occasionally. The 39 upper limestone bed is massive; occasionally large ortho- 40 cerids occur (Temperoceras). The top of K3 is a conspicu- m m 5 41 ous 0.05-m-thick horizon of a limonite-encrusted nodular 5 DS 42 limestone that is interpreted as an omission horizon. 43 Above K3 a claystone succession c. 8 m thick occurs TEXT-FIG. 8. Section of the Pragian and Zlı´chovian 44 (KMO-III), which in its basal part contains a considerable limestones of Filon Douze, Tafilalt. The first ammonoids occur 45 percentage of sand; towards the middle is an interval with in the Erbenoceras Limestone. The earliest occurrences of 46 numerous thin nodular limestone horizons and small fav- Bactrites and Centroceras are in beds KMO-III and KMO-IV 47 ositid biostromes <0.2 m thick and c. 2–3 m in diameter. respectively; for explanation of symbols, see Text-figure 6. 48 This interval is highly fossiliferous containing mainly tri- 49 lobites (Gravicalymene sp., Reedops intermedius, Reedops (mostly pelmatozoan debris) at its base. The dacryonoco- 50 ex. gr. cephalotes, Paralejurus sp.). The cephalopod assem- narids (Nowakia acuaria) are deposited in cone-in-cone 51 blage is dominated by pseudorthocerids, Temperoceras position, but macrofossils are generally very rare. 52 and Arthrophyllum. Above K2 is a monotonous greenish claystone 23 m 53 Limestone K2 is a 0.2-m-thick, massive, biodetrital da- thick in which no macrofossils were found apart from in 54 cryoconarid grainstone, containing more biodetritus the uppermost part, in a horizon c. 0.5–2 m below the 14 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Deiroceras Limestone, where there is a conspicuous con- iens and Mimotornoceras djemeli characterize the lower 2 centration of limonitized macrofossils (bed EF). This part of the interval representing the Chotecˇ Event level 3 horizon is identical to Emsian faunule A horizon of Klug 3(after Chlupa´c 1985). The ammonoid Pinacites jugleri 4 et al. (2008). The fauna consists predominantly of occurs just above the Chotecˇ Event, providing evidence of 5 Devonobactrites obliquiseptatum, trilobites and hyolithids, the jugleri Event of Walliser (1985). The entire interval in 6 and occasionally orthocerids. the Tafilalt was part of a detailed stratigraphical investiga- 7 The Deiroceras Limestone is a massive greyish wacke- tion by Klug (2002). 8 stone 1.5 m thick that contains large (cross-section c. 50– 9 100 mm) fragments of Deiroceras, and rare Devonobac- Thickness. Approximately 2 m. 10 trites. The orthocones are horizontally bedded, but have 11 no preferred orientation. Often the conchs are partly dis- Description. The dark claystones and nodular limestones 12 solved and destroyed at the top, and locally winnowing of of the Chotecˇ Event level (Bed F) mark the onset of a 13 the micritic matrix has occurred, indicating reduced sedi- basic change in the sedimentological regime at Filon Dou- 14 mentation rates. At the top of the Deiroceras limestone ze and in the eastern Anti Atlas Region inclusive of the 15 there is a limestone bed 0.02 m thick that displays an Tafilalt. Above this level the predominantly siliciclastic 16 irregular limonitized, partly phosphoritized surface that is succession with a few intercalated limestone horizons 17 interpreted as an incipient hardground. (‘Amerboh Group’ of Hollard 1981) changes towards 18 Above the Deiroceras Limestone there is a 2.5-m-thick mainly limestones with thin intercalated marls (‘Bou 19 succession of claystones with intercalated nodular bioclas- Tchrafine Group’ of Hollard 1981). 20 tic limestone beds (KMO-IV) that contain a rich fauna of Bed F is composed of a dark, nodular, dacryoconarid 21 rugose corals and trilobites. The cephalopods are less packstone that is intercalated with irregular argillaceous 22 common than in the marls below; Temperoceras and Ar- layers. The entire horizon is 0.6 m thick and successively 23 throphyllum are most frequent. At the top of this interval changes towards a more massive limestone at the top; its 24 the carbonate content increases successively and merges dominant macrofossil is the bivalve Panenka, which 25 with that of the overlying Erbenoceras Limestone. reaches 50 mm in size. The packstones and argillaceous 26 The basal 0.3 m of the Erbenoceras Limestone consists interbeds contain masses of dacryoconarids that are often 27 of argillacaeous nodular limestones that contain abundant deposited in cone-in-cone position. Most nautiloids have 28 large specimens of Panenka. Towards the top, there is a imploded phragmocones with broken septa retained in 29 more massive limestone bed 1.5 m thick containing abun- the conchs. Ammonoids are common but usually frag- 30 dant orthocerids. The agoniatitid Erbenoceras advolvens is mentary. They are dominated by agoniatids. Klug (2002) 31 a conspicuous element of this horizon. The entire Erbe- reported five agoniatitid species in bed F from the Jebel 32 noceras Limestone is about 4.5 m thick, with an increas- Ouaoufilal East. In addition to the ammonoids, Neocyc- 33 ing number of fine argillaceous layers towards the top. loceras and oncocerids are conspicuous elements of bed F. 34 The limestones are nodular, biodetrital wacke-packstones Above this bed is a 1-m-thick, massive, dark grey da- 35 containing predominantly pelmatozoan debris and da- cryoconarid packstone–floatstone that consists of two 36 cryoconarids. Klug (2002) reported Nowakia zlichovenis conspicuous, exceptionally fossil-rich layers at 0.2 m (PI) 37 magrebiana, N. praesulcata, N. cf. kabylica and the trilo- and 0.7 m (PII) from the base. Klug (2002) reported that 38 bite Sculptoproteus magrebus from it. Cephalopods are the horizon is composed of two conspicuous fossiliferous 39 common in the upper part of these limestones; ortho- layers throughout the Tafilalt and noted that several iron- 40 cones such as Metarmenoceras, Subormoceras gen. nov. rich bands occur in the limestone, and a sometimes win- 41 and Devonobactrites are most frequent. Large fragments of nowed micritic matrix between the biodetrital compo- 42 Metarmenoceras with cross-sections of 150–200 mm occur nents indicates condensed sedimentation; ammonoids are 43 in the uppermost interval of the limestones together with the dominant macrofossils. Klug (2002) reported eight 44 abundant bivalves (predominantly Panenk). species of agoniatitids and four species of anarcestids 45 The c. 125-m-thick Emsian claystones that overlie the from the Jebel Ouaoufilal East section, and emphasized 46 Erbenoceras Limestone are poorly exposed at Filon that the ammonoid layers are composed exclusively of 47 Douze. either anarcestids or agoniatitids. Bactritoids are the next 48 most common cephalopods in PI and PII; slender ortho- 49 cerids such as Infundibuloceras occur. The pseudortho- 50 5. Early Eifelian limestone succession ceratid Subormoceras is relatively common. The 51 bactritoids and orthocerids are clearly orientated in a 52 Biostratigraphy. Late Pedavis patulus conodont Biozone– north-east–south-west direction. A dominant direction of 53 early Oneotodus costatus conodont Biozone, early–middle the apical position was impossible to detect at Filon 54 Eifelian (after Klug 2002). The ammonoids Foordites ven- Douze, rendering the origin of the currents somewhat 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 15

1 uncertain. A rich benthic fauna of gastropods, trilobites In conclusion, the sedimentary succession of the Filon 2 and bivalves characterizes this limestone bed. Douze section is consistent with the eustatic curve pre- 3 sented by Johnson et al. (1985) and Buggisch and Mann 4 (2004, fig. 13) with major sequence boundaries around 5 INTERPRETATION OF THE the Silurian ⁄ Devonian boundary, the Lochkovian ⁄ Pragian 6 SEDIMENTARY SUCCESSION boundary, and in the upper Dalejian. 7 8 General remarks 9 Description of depositional cycles 10 The sedimentary succession is dominated by thick clay- 11 stones, which are intercalated by horizons of limestones, The lowermost cycle of the measured section is the mas- 12 siltstones and sandstones. It represents a mixed carbon- sive limestone of bed OP and the overlying tempestitic 13 ate-siliciclastic system on the continental shelf of northern bed OP-K, which is interpreted as representing a shallow- 14 Gondwana. The lack of turbidites is interpreted as evi- ing sequence of the highstand systems (Text-fig. 9). 15 dence for a very gently sloping sea-floor. A predominantly The base of the subsequent cycle is placed at the base 16 E ⁄ W–NE ⁄ SW orientation of orthocones reflects a shore- of the sandstone at the top of the Temperoceras limestone 17 line-parallel current regime at times of orthocone succession. The subsequent transgression of the second 18 deposition (compare with the palaeogeographical recon- cycle is recorded by a decrease in sand and silt content of 19 structions of Legrand 2003). the claystones. An interval within the claystone, c.30m 20 The limestone and sandstone horizons, which are inter- above the base of the sandstone, commonly containing 21 calated within the claystones, mark the boundaries of five sideritic nodules, is interpreted as a maximum flooding 22 main depositional cycles. At the base of each cycle arenit- horizon. The Scyphocrinites limestone succession, which is 23 ic and tempestite horizons occur; the top of some cycles composed of proximal tempestites and calcarenites, is 24 show massive limestone beds. Quartz arenites, siltstones interpreted as a shallowing-up sequence representing the 25 and tempestites are interpreted as representing lowstands. highstand systems tract of the second cycle. The top of 26 Sideritic and phosphoritic nodular horizons within the this shallowing-upwards sequence is the crinoidal calcare- 27 claystones (bed PK) and claystones containing secondarily nite bed C, which is regarded as the base of the third

28 limonitized pyrite nodules and limonitized fossils are cycle and correlates with cycle Ia2 of Buggisch and Mann 29 interpreted as representing a reduced sedimentation rate (2004). 30 when sea-level rise was rapid during transgressions. Gen- The transgression of the third cycle is recorded by a 31 erally, the claystone beds contain a higher silt fraction at thick succession of partly well-laminated claystones. The 32 the base of each sedimentary cycle. nodular bed PK within these claystones is interpreted as a 33 No continuous trend of deepening or shallowing of the maximum flooding horizon. The tempestites and argilla- 34 depth of deposition through the succession can be detected. ceous sandstones of the Jovellania limestone succession 35 Sandstones occur at the top of the Temperoceras and Jovell- are interpreted as representing the progradation of clastic 36 ania limestone successions, and some horizons within the sediment within the highstand systems tract of the third 37 Pragian limestone succession contain a considerable per- cycle. 38 centage of quartz sand. Proximal tempestites occur within The fourth cycle, which can be correlated with deposi-

39 the Temperoceras, Scyphocrinites, Jovellania, and Pragian tional cycle Ia1 of Buggisch and Mann (2004), begins at 40 and Zlı´chovian limestone successions. Deep erosional the base of sandstone DS at the top of the Jovellania lime- 41 structures at the base of the pre-Pragian tempestites and stone succession. The decreasing quartz and silt content 42 their coarser components indicate a higher energy regime of the subsequent marl-limestone alternations indicates a 43 during deposition, which is attributed to their generally deepening of the depositional setting. Limestone K3, 44 shallower depths of deposition compared to the Pragian– which shows a conspicuous omission horizon at the top 45 Eifelian beds. By contrast, the post-Lochkovian sediments and contains a considerable fraction of sand, is inter- 46 (including the tempestites) contain a considerably richer preted as the base of the fifth cycle. 47 benthos, indicating shallower depositional conditions com- Within the fifth cycle, which can be correlated with 48 pared with Ludlow–Lochkovian sediments, and the occur- cycles Ib and Ic of Johnson et al. (1985) and Buggisch 49 rence of small favositid bioherms within Zlı´chovian marls and Mann (2004), four subordinate cycles can be distin- 50 and claystones indicates deposition within the photic zone. guished. The lowermost subcycle consists of a thick clay- 51 However, the lack of benthos, except for epibyssate bivalves stone that contains at its top a conspicuous limonitized 52 within pre-Pragian sediments, is not a sufficient argument fauna (bed EF) and limonite nodules. Bed EF is inter- 53 for deeper depositional settings; I interpret it as evidence preted as the maximum flooding horizon of this subcycle. 54 for reduced bottom oxygenation. The overlying Deiroceras Limestone shows evidence of 16 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Discocerida Nautilida Oncocerida 2 3

gen.nov.

4 v.

M.2001 .no gen.nov. nov. gen.nov. 5 indet. A gen.nov. gen Flower 1938 gen. 6 Zhur.1974 Hyatt 1884 depositional depositional Bayle 1879 7 sequences depth eras 8 base storm waves shallow deep PseudendoplectocerasOrthorizoceras Ankyloceras Jovellania BohemojovellaniaTafilaltoceras VentrobalasoviaMutoblakeoceras Nothoceratidae Brevicoc Cerovoceras Centroceras 9 Eifelian Pinacites Limestone 10 11 12 13 14 15 16 17 Dalejian 18 19 20 21 22 Erbenoceras Limestone Deiroceras Limestone 23 (= ‘Jovellania Limestone’ Zlichovian 24 of Bultynck and Walliser, 1999) 25 cycle V Devonian

26 Pragian cycle IV 27 Jovellania limestone s. 28 29 30 31 32 33 34 Lochkovian 35 PK 36 37 38 cycle III 39 Scyphocrinites limestone s. 40 41 42

43 Pridolian 44 45 Silurian 46 47 cycle II 100 m Ludfordian Temperoceras limestone s. 48 cycle I 49 50 TEXT-FIG. 9. The complete section at Filon Douze showing limits of depositional sequences, reconstructed depositional depth, and 51 stratigraphical ranges of the non-ammonoid cephalopods illustrated. 52 53 54 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 17

1 Arionoceratidae Sichuanoceratidae Lituitida Sphaerorthoceratidae 2 Actinocerida Dawsonoc. Orthoceratidae Geisonoc. Sphooc. Pseudorthocerida Bact. 3 Kionoc. 4 t. 1968

Rist. 1968 Rist. 1968 5 Ris gen.nov. . 1978 T. & G. 1952 Rist. 1968 FI. 1940 gen.nov. gen.nov. Barsk. 1972 gen.nov. Shim. 1972 6 Forest. 1932 Forest. 1932Kies. 1969 Sh. & Ob. 1935 Chang 1962 gen.nov. FI. & Cast. 1935 Barsk. 1960 gen.nov. gen.nov. Bey. 1850 gen.nov. Zhur. 1978 gen.nov. Schindew. 1932 gen.nov. Barsk. 1966 FI. 1962 Stokes 1840 Hyatt 1884 Hyatt 1884 7 Hyatt gen.nov. Manda 2001 8 Sandberger 1843 9 10 Ormoceras Deiroceras MetarmenocerasSubormoceras Spyroceras SubdolocerasReticuloceras Probatoceras Geidoloceras Zhur Suloceras NeocyclocerasArthrophyllum Michelinoceras Kopaninoceras Plagiostomoceras Merocycloceras Orthocycloceras Rist. 1968Tibichoanoceras Pseudospyroceras Chebbioceras Infundibuloceras Bogoslovskya Theoceras ArionocerasParakionoceras Adiagoceras Anaspyroceras Temperoceras Angeisonoceras Kionoceras SichuanocerasHemicosmorthoceras Parasphaerorthoceras Akrosphaerorthoceras Sphaerorthoceras Sphooceras Devonobactrites Bactrites Lobobactrites 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

50 TEXT-FIG. 9. Continued. 51 52 reduced sedimentation rates and a conspicuous hard- consists of several metres of claystones at its base, includ- 53 ground at the top. This hardground is interpreted as the ing small Favosites bioherms, which merge smoothly 54 boundary with the second subcycle. The second subcycle towards nodular limestones at the base of the Erbenoceras 18 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Limestone. The overlying middle part of this limestone is Bactritida and Nautilida. The taxonomic distinctness is 2 a condensed biodetrital wackestone with several incon- not a proxy of disparity, because genera such as Arthro- 3 spicuous omission horizons. The boundary with the phyllum and Bactrites are orthocones, showing similar 4 uppermost subcycle of the fifth cycle is placed at the mid- morphology to other orthocones of the Orthocerida, but 5 dle of the Erbenoceras Limestone, which towards its top represent different higher taxa. Therefore, the taxonomic 6 merges into a nodular argillaceous wackestone. A thick distinctness provides no estimate of the disparity of the 7 succession of claystones marks the lower part of the cephalopod fauna. However, the occurrence of brevicones 8 uppermost subcycle of the fifth depositional cycle. The and coiled nautiloids in the post-Lochkovian strata of the 9 carbonate content of these claystones increases towards Filon Douze section is evidence for an increased disparity 10 the top and the higher part of the beds is composed of in the Pragian–Middle Devonian compared with the Silu- 11 an alternation of nodular limestones and claystones. The rian and lowest Devonian. Remarkably, this increase in 12 dark nodular dacryoconarid packstone of the transgressive disparity and taxonomic distinctness occurs below the sig- 13 Chotecˇ event (Klug 2002) terminates the fifth cycle. nificant Lochkovian–Pragian facies change at Filon Douze. 14 Because no data from other localities of that time interval 15 are available, it is impossible to compare the diversity 16 CEPHALOPOD SUCCESSION trends with a supra-regional pattern. 17 Besides the low evenness values of beds PK and EF no 18 Diversity signal trend in change of evenness can be detected in the sec- 19 tion. The low evenness values of beds PK and EF reflect 20 On average the cephalopod-bearing beds of the Filon the strong dominance of Plagiostomoceras and Devonobac- 21 Douze section each contain seven species belonging to six trites respectively; it is interpreted as reflecting the deep 22 genera (ammonoids excluded). The Deiroceras limestone depositional environment of these beds. Accordingly, 23 is the only monospecific bed, containing exclusively Dei- these two genera are interpreted as being orthocones that 24 roceras hollardi gen. et sp. nov. The richest cephalopod 25 fauna recovered, containing a total of 17 species belong- diversity measures + ‚ 26 ing to 13 genera, is from the tempestite bed OJ-I. The Chao 1 ∆ H 100 m 5 15 25 2.5 3.5 0.75 2.25 27 results of standardized diversity estimation show excep- Eifelian jugleri lst. 28 tionally low values for the Chao I richness estimator for

29 beds PK (Schao1 = 4) and EF (Schao1 = 5) (Text-fig. 10; 30 Table 1). The associations of both beds are preserved in 31 clay-siltstones and are interpreted as representing the Dalejian 32 deepest depositional environments of the Filon Douze 33 section (see above). In bed PK the cephalopod fauna is Zlich- Erbenoceras Lst. 34 dominated by Plagiostomoceras, in bed EF by Devonobac- ovian 35 trites. Both low diversity values are supported by a high Pragian 36 number of samples. In contrast, the highest estimated Jovellania Lst.

37 Chao 1 richness occurs in the Pragian marl KMO-III Devonian

38 (Schao1 = 25). However, the richness is only slightly lower 39 in other Pragian marls and in the tempestitic coquininas Loch- 40 OP-M (Schao1 = 21) and OJ-I (Schao1 = 18). There is no kovian 41 general trend of increasing or decreasing richness during PK 42 the observed interval. Scyphocrinites Lst. 43 The measure of taxonomic distinctness is independent Prido- 44 of sample size. Therefore, those beds containing more lian 45 than two species of cephalopods are sufficient for taxo- 46 nomic distinctness calculations. The results show that a Lud- Silurian fordian 47 significant increase in taxonomic distinctness values from Temperoceras Lst. 48 D+=2.5 towards values of D+>3.25 occurs with the onset TEXT-FIG. 10. Diversity measures of selected beds in the 49 of the Jovellania limestone succession (Text-fig. 10; Filon Douze section. SChao 1, species richness after Chao (1984) 50 Table 4). Whilst the Temperoceras and Scyphocrinites lime- with bars indicating 95 per cent confidence level; D+, taxonomic 51 stone successions contain almost exclusively Orthocerida distinctness after Clarke and Warwick (1998, 1999); H’, Shannon 52 and rarely Pseudorthocerida or Oncocerida, the Jovellania index. Note the distinct increase in all values within and above 53 limestone succession and higher beds are characterized by the Jovellania limestone succession. Very low diversity and 54 an additional modest content of Discosorida, Lituitida, evenness values occur in bed PK and EF. For data, see Table 1. 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 19

1 inhabited distal environments, probably in a pseudo- TABLE 4. Orthocone cephalopods of the Filon Douze section 2 planktonic lifestyle. classified as angustocones or euorthocones. Euorthocones have 3 comparatively large siphuncles, endosiphuncular and often heavy 4 cameral deposits. Angustocones have narrow siphuncles, sup- pressed endosiphuncular and cameral deposits and often slender 5 Morphological signal conchs with wide septal spacing. 6 7 Orthocones dominate the cephalopods in the succession. Order Genus Angustocone Euorthocone 8 Two groups can be distinguished. The first comprises Actinocerida Metarmenoceras x 9 those with a comparatively high angle of expansion, wide Ormoceras x 10 siphuncle that may be expanded within the chambers, Deiroceras x 11 and massive cameral and endosiphuncular deposits; repre- Pseudorthocerida Diagoceras x 12 sentatives are the Actinoceratida, Pseudorthoceratida, and Geidoloceras x 13 Geisonoceratidae such as Temperoceras. Arthrophyllum Neocycloceras x 14 also belongs here (Table 4). I include these forms within Probatoceras x 15 the euorthocones (new term). The second group com- Reticuloceras x 16 prises slender, often small conchs, with a narrow siphun- gen. nov. 17 cle, often having wide septal spacing. Cameral and Subdoloceras x 18 endosiphuncular deposits are suppressed or lacking in gen. nov. 19 these conchs. Representatives are Arionoceratidae, Or- Subormoceras x gen. nov. 20 thoceratidae and bactritoids, which I include in the angu- Spyroceras x 21 stocones (new term). Plagiostomoceras is assigned to the Cancellpyroceras x 22 angustocones, although the type species has cameral gen. nov. 23 deposits. This is justified as all the species occurring in Suloceras x 24 the Filon Douze section have slender shells with a narrow Lituitida Arthrophyllum x 25 siphuncle and without deposits. Their narrow siphuncle Sphooceras x 26 indicates a low cost for buoyancy regulation and suggests Orthocerida Chebbioceras x 27 an energy-intensive lifestyle (see Kro¨ger 2003). The lack Infundibuloceras x 28 of cameral deposits is probably an effect of a reduced Kopaninoceras x 29 liquid passage through the phragmocone during life. They Merocycloceras x 30 are interpreted as cephalopods with low energy needs, Michelinoceras x Orthocycloceras x 31 adapted to environments with low food availability that Plagiostomoceras x 32 lived as vertical migrants in the free water column. As the Pseudospyroceras x 33 distal environments of the free water column are rela- gen. nov. 34 tively poor in food availability, angustocones are inter- Theoceras x 35 preted as planktonic dwellers. gen. nov. 36 In contrast, euorthocones are interpreted as cephalo- Tibichoanoceras x 37 pods with a comparatively energy-intensive lifestyle; they gen. nov. 38 potentially were also active vertical migrants. Increased Arionoceras x 39 internal cameral surfaces in many forms and the compar- Adiagoceras x 40 atively large siphuncular surface are evidence for an abil- gen. nov. 41 ity actively to regulate buoyancy. However, buoyancy Parakionoceras x Anaspyroceras X 42 regulation of the euorthocones was much more cost- Angeisonoceras X 43 intensive than that in angustocones, demanding more gen. nov. 44 active searching for high energy food. The increased sip- Temperoceras X 45 huncular surface must have caused comparatively high- Kionoceras x 46 cost buoyancy regulation (see Kro¨ger 2003). A demersal Sichuanoceras X 47 lifestyle of euorthocones, probably comparable to that of Sphaerorthoceras x 48 the recent Nautilus, is inferred from this evidence. Akrosphaerorthoceras x 49 When comparing the relationship of the richness of Parasphaerorthoceras x 50 these two groups in the individual beds at Filon Douze a Hemicosmorthoceras x 51 clear pattern is visible (Text-fig. 11). The pre-Pragian Bacritida Bactrites x 52 beds EF and F have very low percentages of euorthocones, Devonobactrites x Lobobactrites x 53 whereas they are the dominant group in the Pragian– 54 Middle Devonian beds. Bed EF is a clay-siltstone horizon 20 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 containing a rich benthic and nectonic limonitized fauna 0.2 0.4 0.6 0.8 1 2 including trilobites, gastropods and acanthodians (Klug P 3 et al. 2008). Bed F with a dark marl to nodular limestone F 4 lithology has masses of dacryoconarids, representing the KMO-V 5 Chotecˇ transgressive event (see Klug 2002). Bed PK, Erb. Lst. 6 which yields exclusively angustocones (Plagiostomoceras KMO-IV 7 culter, Hemicosmorthoceras semimbricatum) is a limestone Deir. Lst. 8 nodule horizon within platy claystones–siltstones that EF 9 commonly contains graptolites underneath angustocone KMO-III KMO-II 10 orthocones and a low diversity fauna of epibyssate bival- KMO-I 11 ves. Beds PK, EF and F are interpreted as representing the OJ-II 12 deepest, most distal depositional settings of the section CK 13 during maximum flooding intervals. The strong domi- BS 14 nance of angustocones in these beds supports the sug- OJ-I 15 gested planktonic, energy-intensive lifestyle of these PK 16 forms. A similar concentration of angustocones has been OSP-I 17 reported from distal environments in the Ludlow type OP-M 18 area (Hewitt and Watkins 1980), where Arionoceras grega- 0.2 0.4 0.6 0.8 1 19 rium and Hemicosmorthoceras dimidiatum are the domi- TEXT-FIG. 11. Ratio of species richness of 20 nant taxa. Wilmsen (2006) reported the occurrence of euorthocone ⁄ angustocone orthocerids in selected beds of the 21 frequency peaks of organisms adapted to low food avail- Filon Douze section. Note the distinct increase in the ratio 22 ability during maximum flooding intervals within the above the Jovellania limestone succession (bed OJ-II) and the 23 boreal Upper Cretaceous limestones of central Europe. A low values for beds EF and F. For data, see Table 1. 24 similar faunal pattern occurs in the Siluro-Devonian 25 strata of the Tafilalt. 26 Euorthocones are generally strongly under-represented Krˇı´zˇ (1998, 1999) reported the disappearance of the 27 in all pre-Pragian beds and the benthos indicates oxygen- orthocone-bivalve community that is typical of Silurian– 28 poor conditions at the bottom which, however, are not earliest Devonian successions world-wide at the end of 29 entirely linked with depth of deposition. Althought beds the Lochkovian, and an increased benthic diversity and 30 PK, EF and F represent comparatively deep conditions colour change towards lighter sediment colours above the 31 below storm wave-base, the fauna of the pre-Pragian tem- Lochkovian ⁄ Pragian has been reported from the Barran- 32 pestites and sandstones was deposited under shallow con- dian area (Chlupa´cˇ et al. 2000), the Carnic Alps (Scho¨n- 33 ditions above storm wave-base. The depositional depths laub 1996) and the Iberian Massifs (Garcia-Alcalde et al. 34 recorded at Filon Douze are in good accordance with 2000; Robardet and Gutie´rrez-Marco 2004). A major car- 35 supra-regional sea-level curves (Johnson et al. 1985; Bug- bon isotope shift was recorded by Buggisch and Mann 36 gisch and Mann 2004) in which the Pragian eustatic sea (2004) at the Lochkovian ⁄ Pragian transition in central 37 level is not significantly lower compared with the Lochko- and southern Europe. Additionally, a clear shift from low 38 vian. Nevertheless, tempestites and sandstones contain diversity orthocerid-bivalve-dominated palaeocommuni- 39 few euorthocones and a restricted benthos largely com- ties towards palaeocommunities containing a rich benthos 40 posed of epibyssate bivalves. 4has been reported from Sardinia (Ferreti et al. 1999).A 41 The faunal composition dramatically changes at the radiation of pseudorthocerids and non-orthocone, non- 42 base of the Pragian above bed OJ-II. The entire upper ammonoid cephalopods occurs in post-Lochkovian lime- 43 part of the section is composed of a diverse benthos and stones in the Barrandian (Manda 2001). The trend visible 44 a predominance of euorthocones, even in parts that are at Filon Douze et al.appears, therefore, to be representa- 45 interpreted as deposited below storm wave-base, such as tive of a wider range of peri-Gondwanan areas of the Pal- 46 the marl beds KMO-I, II, and III. This faunal change is aeo-Tethys. The poorly oxygenated bottom conditions 47 accompanied by a marked change in sediment colour even in shallow-water settings that characterized long 48 from black or dark brown to light brown or yellowish. intervals in the Silurian and earliest Devonian disappeared 49 Dramatic faunal and sedimentary colour changes are suddenly in the Pragian and culminated in the establish- 50 not restricted to the Filon Douze section. Alberti (1980), ment of carbonate platforms in the Emsian and Middle 51 Belka et al. (1999), and Bultynck and Walliser (2000, p. Devonian. At Filon Douze a change in the non-ammo- 52 216) recorded the disappearance of black sediments above noid cephalopod fauna corresponds with this trend, lead- 53 the uppermost ‘Orthoceras’ Limestone in proximity to the ing from faunas dominated by angustocones to those 54 Lochkovian ⁄ Pragian boundary in the northern Tafilalt. dominated by euorthocones. 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 21

1 Evolutionary signal sively an elliptical protoconch apical of a slender conch, 2 which over a significant initial distance is narrower in 3 The top of the Jovellania limestone succession, which cross-section than the relatively large protoconch (cross- 4 marks the Lochkovian ⁄ Pragian boundary, coincides with section c. 0.5 mm). ‘Bactrites’ bohemicus contrasts markedly 5 the disappearance of a number of characteristic Silurian with these later forms and is more similar in apical shape to 6 cephalopods at Filon Douze. Hemicosmorthoceras, Ak- the mid Silurian Sphaerorthoceras beatum, S. carnicum and 7 rosphaerorthoceras, Arionoceras and Parakionoceras have S. teicherti (all Ristedt, 1968). Instead, the apex of the Devo- 8 their last occurrence in the limestone, and are not nian bactritoids strongly resembles the apices of the Middle 9 reported to occur in younger beds elsewhere. The subse- Silurian ‘Sphaerorthoceras’ spp. A–C and E–F described by 10 quent Pragian strata contain a cephalopod fauna that is Ristedt (1968) and the Early Devonian Protobactrites? sp. 11 characterized by a high number of endemic genera, and (Serpagli and Gnoli 1977, text-figs 5–6). These latter forms 12 genera known exclusively from the late Early Devonian have a protoconch that is larger in cross-section than the 13 and early Middle Devonian, such as many pseudorthocer- subsequent slender conch. The commonality of apical 14 ids and Arthrophyllum. No major new group appears in shape, apical dimension and eccentricity of the siphuncle in 15 the Pragian beds of Filon Douze. the case of Protobactrites is a strong argument for a phylo- 16 A strong evolutionary pulse occurs in the Zlı´chovian, in genetic lineage leading to the Devonian bactritoids (Kro¨ger 17 which many new genera first occur and major new groups, 2007). Therefore, an origin of bactritoids not earlier than 18 such as bactritoids, ammonoids and nautilitids, suddenly Pragian is highly probable. 19 appear. Bactritoids appear at Filon Douze in the lower Zlı´- Beneath the first appearance of bactritoids in the Pra- 20 chovian (Devonobactrites obliquum). Only a single ques- gian and ammonoids in the Zlı´chovian, the first tightly 21 tionable fragment of a bactritoid was found in pre-Emsian coiled representative of the Nautilitida is Centroceras sp. 22 strata (KMO-III, Pragian). This local result reflects a gen- in bed KMO-IV in the Zlı´chovian. The occurrence of 23 eral observation. Despite intensive collecting effort and Centroceras at Filon Douze is the earliest occurrence of a 24 repeated monographic treatment of Siluro-Devonian ceph- tightly coiled nautilid anywhere; it marks the initial 25 alopod faunules, no additional bactritoid specimens have appearance of a group of coiled nautiloids that domi- 26 been reported in pre-Emsian strata since the work of Rist- nated the Late Palaeozoic and persists with Recent Nauti- 27 edt (1981). A single poorly preserved and insufficiently lus. The phylogeny of early nautilids is problematic; Dzik 28 illustrated bactritoid was reported by Termier and Termier and Korn (1992) considered openly coiled Pragian onco- 29 (1950, pl. 87, figs 27–29) from the Upper Silurian of the cerids or trochospiral lechritrochocerids as possible ances- 30 Tafilalt east of Erfoud. Holland (2003) noted that this spec- tors. The first tightly coiled planispiral nautiloids are now 31 imen should at best be disregarded. Thus, it appears that known from the Early Emsian. 32 bactritoid orthocones are very rare or absent in pre-Emsian In conclusion, the stratigraphical pattern apparent at 33 strata with the exception of ‘Bactrites’ bohemicus. However, the Filon Douze section indicates an evolutionary pulse 34 although assigned to Bactrites, the Ludlovian ‘B.’ bohemicus with the onset of several high level taxa in the late Pra- 35 was regarded as an early Zlı´chovian homoeomorph of the gian–Early Emsian. It occurs considerably above the 36 Devonian Bactrites by Ristedt (1981). New data of the api- major facies change at the base of the Pragian. 37 cal morphology of Devonobactrites from the lower Zlı´cho- 38 vian at Filon Douze support his opinion. The protoconch 39 of Devonobactrites is elliptical, egg-shaped, and the conch SYSTEMATIC PALAEONTOLOGY 40 adoral of the apical chamber is slender and displays a cross- 41 section diameter less than that of the protoconch. This Institutional abbreviations. MB.C., Museum fu¨r Naturkunde Ber- 42 morphology is similar to the apex known from Bactrites lin; PIMUZ, Pala¨ontologisches Museum and Institut, Universita¨t 43 gracilis (Blumenbach, 1803) (= Orthoceras schlotheimii Zu¨rich. 44 Quenstedt, 1845; compare Kro¨ger et al. 2005). Therefore, 45 the apical shape of Bactrites gracilis differs from that of ‘B.’ 46 bohemicus in which the protoconch is subspherical and has Class CEPHALOPODA Cuvier, 1797 47 a smaller diameter than the subsequent conch section. Order DISCOSORIDA Flower, in Flower and Kummel 1950 48 Moreover, the protoconch of ‘B.’ bohemicus is about Family PHRAGMOCERATIDAE Miller, 1877 49 0.2 mm in length and cross-section whereas that of 50 Devonobactrites obliquum is 0.8 mm long and 0.4 mm in Genus PSEUDENDOPLECTOCERAS gen. nov. 51 diameter. The dimensions of the latter are similar to those 52 of protoconchs of Middle Devonian bactritoids (see Erben Type species. Pseudendoplectoceras lahcani sp. nov., from the Pra- 53 1960) and early ammonoids (see Erben 1964). Thus, the gian of the Filon Douze section. 54 available data show that Devonian bactritoids have exclu- 22 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Derivation of name. Greek, ‘pseudes, false, because the new genus (Pl. 16, figs 9–11). Siphuncular segments only slightly 2 resembles Endoplectoceras. expanded. Siphuncle more expanded at adoral part of each 3 segment. Endosiphuncular deposits elongated in apical 4 Other species included. None. direction. 5 6 Diagnosis. Trochoceroid phragmoceratid with circular or Occurrence. As for genus. 7 slightly compressed cross-section and marginal siphuncle 8 on concave side of shell curvature; angle of expansion c. 9 15 degrees; shell surface with faint straight, transverse Order ONCOCERIDA Flower, in Flower and Kummel 1950 10 growth lines and very shallow irregular undulations; sip- Family BREVICOCERATIDAE Flower, 1945 11 huncle large with diameter 0.3 of conch cross-section; 12 nummoidal siphuncular segments weakly expanded Genus BREVICOCERAS Flower, 1938 13 within chambers; adoral parts of siphuncular segments Type species. Brevicoceras casteri Flower, 1938, from the Windom 14 more strongly expanded than adapical parts; endosiphun- cular deposits form adapically elongated bullettes. Member, Moscow Formation, Middle Devonian, of Filmore 15 Glen, Moravia, New York, USA. 16 Remarks. This genus is similar to the mid Silurian Endo- 17 Diagnosis (from Flower 1938, p. 24). Slightly cyrtoconic plectoceras Foerste, 1926, in general conch shape, but dif- 18 brevicones with depressed cross-section; in early growth fers in having more strongly expanded siphuncular 19 stages prosiphuncular side slightly more rounded than segments with a simple convex connecting ring. The 20 dorsum; near base of mature living chamber antisiphun- conch of Endoplectoceras differs further in being more 21 cular side flattened; near aperture cross-section rounded compressed and less strongly coiled. 22 subtriangular with flattened antisiphuncular side; in dor- 23 Occurrence. Pragian; Morocco. soventral direction prosiphuncular side convex, antisip- 24 huncular side adapically concave, convex until base of 25 mature body chamber, straight or only faintly convex 26 until mature peristome; adjacent body chamber straight 27 Pseudendoplectoceras lahcani sp. nov. Plate 1, figures 1–4; Plate 16, figures 9–11 or faintly concave, close to peristome; position of largest 28 gibbosity varies from species to species but generally at 29 base of body chamber to adoral part of phragmocone in 30 Derivation of name. In honour of Filon Douze miner Lahcan Caraoui. mature specimen; septa shallow and evenly curved; 31 sutures sinuous with broad shallow lobes, lateral saddles 32 Holotype. MB.C.10184 (Pl. 16, figs 9–11). and conspicuous lobe on antisiphuncular side; siphuncle 33 nummoidal; actinosiphuncular deposits occur. 34 Type locality and horizon. Filon Douze section, bed KMO-II, 35 Pragian. Occurrence. Middle–Late Devonian; Morocco, North America 36 and Russia. 37 Other material. 9 fragments from the type locality and horizon. 38 39 Diagnosis. As for genus. Brevicoceras magnum sp. nov. 40 Plate 1, figures 5–7; Text-figure 12A–C 41 Description. Conch trochoceroid, lateral shift of coiling axis of 42 <5 mm across coiling of 180 degrees in MB.C.10185 with Derivation of name. Latin, magnus, large, referring to the adult 43 smaller diameter 10 mm; larger diameter c. 24 mm and length size of this Brevicoceras. 44 of coiling axis of c. 49 mm. Largest fragment, MB.C.10187, 45 with dorsoventral cross-section of c. 40 mm. Conch circular Holotype. MB.C.9632 (Pl. 1, figs 5–7). 46 or slightly compressed with ratio of conch width to height c. 47 0.9. Conch surface ornamented with distinct transverse, irregu- Type locality and horizon. Filon Douze section, bed PI, early O. larly but narrowly spaced growth lines and shallow, directly 48 costatus conodont Biozone, middle Eifelian. transverse, irregularly spaced undulations. Septal distance at 49 conch diameter of 25 mm, 2.5 mm. Septal perforation mar- Other material. Known only from the holotype. 50 ginal with elliptically compressed cross-section; 3.8 mm wide 51 and 5 mm high at conch diameter 21.7 mm in MB.C.10188. Diagnosis. Brevicoceras with adult size of c. 40 mm in 52 Septal necks strongly recumbent, touching adapical surface of 53 septa at side of septum, directed towards conch centre, loxo- conch height; shell surface faintly undulating, with con- 54 choanitic on siphuncular side, directed towards conch margin spicuous, irregularly spaced growth lines; cross-section 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 A BC 19 20 21 22 23 24 25 26 27 28 29 30 31 32 D EF 33 34 35 36 37 38 39 40 41 42 43 44 GH I 45 10 mm 46 TEXT-FIG. 12. Reconstructions of Eifelian Brevicoceratidae from Filon Douze. A–C, Brevicoceras magnum sp. nov.; MB.C.9632. A, 47 lateral, B, ventral and C, adoral views. Cerovoceras brevidomus gen. et sp. nov.; MB.C.9620. D, lateral, E, ventral and F, adoral views. 48 G–I, Cerovoceras fatimcaraouii gen. et sp. nov.; MB.C.9623. G, lateral, H, ventral and I, adoral views. Note the characteristic shape of 49 the body chamber horn, and the general shape of the body chamber. Hatched line marks position of siphuncle. Scale bar represents 50 10 mm. 51 52 slightly depressed; length of mature body chamber c. chamber contracted with straight or slightly concave 53 35 mm and height c. 40 mm; aperture broadly elliptical conch margin on antisiphuncular side and convex on 54 with more rounded prosiphuncular side; adjacent body prosiphuncular side in lateral view. 24 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Description. Conch surface slightly irregularly undulating with only at prosiphuncular half; antisiphuncular side shorter 2 distinctive growth lines that are regularly spaced in adapical parts. and carrying conspicuous shallow, subtriangular projec- 3 Distance between growth lines 1 mm. Mature aperture preserved tion, or horn; in median section prosiphuncular conch 4 in fragments. Cross-section of aperture broadly elliptical; width side convex, antisiphuncular nearly straight or faintly 5 37 mm, height 24 mm; prosiphuncular side more rounded. Adoral convex at base of body chamber towards horn; at position 12 mm of body chamber contracted with slightly concave outline 6 of horn, body chamber constricted, forming wide, slightly in dorsoventral view. At base of mould of body chamber numerous 7 broad, shallow, longitudinal striae represent muscle impressions elongated, apertural opening; position of largest gibbosity 8 (Pl. 1, fig. 5). Septa strongly concave with curvature of 11 mm. at base close to most adoral part of phragmocone in 9 Septal distance 9 mm at adoral part of phragmocone, 6 mm at api- mature specimens; septa oblique, sloping in apical direc- 10 cal part of fragment. Sutures form shallow lateral lobes. tion on prosiphuncular side; sutures straight; septal cur- 11 vature shallow; siphuncle close to conch margin; septal 12 Remarks. B. casteri, which is similar in adult size, differs perforation ovate, compressed in type species. 13 in that the adoral part of the body chamber is longer and 14 more elongated. Other species of Brevicoceras are smaller Remarks. The shape of adapical growth stages and characters 15 than B. magnum. of septal necks of Cerovoceras are not known. Its assignment 16 to the Brevicoceratidae is justified by its strong similarity to 17 Occurrence. Middle Eifelian; Morocco. other Brevicoceratidea such as Ovoceras and Brevicoceras 18 Flower, 1936, from which it differs mainly in having a con- 19 spicuous subtriangular body chamber projection. 20 Genus CEROVOCERAS gen. nov. 21 Occurrence. Eifelian; Morocco. 22 Type species. Cerovoceras fatimi sp. nov., from the middle Eif- 23 elian, Filon Douze section. 24 Cerovoceras fatimi sp. nov. 25 Derivation of name. Latin, cerus, horn, referring to the conspicu- Plate 1, figures 9–10, 14; Text-figure 12G–I 26 ous horned body chamber and resemblance to Ovoceras Flower, 27 1936. Derivation of name. In honour of Fatim, son of Filon Douze 28 miner Lahcan Caraoui. Other species included. None. 29 30 Holotype. MB.C.9623 (Pl. 1, figs 9–10, 14). Diagnosis. Brevicones with conspicuous horn on antisip- 31 huncular side of body chamber; cross-section subcircular, 32 Type locality and horizon. Filon Douze section, bed PI, early O. slightly depressed or compressed; body chamber shorter costatus conodont Biozone, middle Eifelian. 33 than wide; mature aperture rounded-subtriangular with 34 flattened antisiphuncular side; it opens body chamber Other material. Known only from the holotype. 35 36 37 38 39 EXPLANATION OF PLATE 1 40 Figs 1–4. Pseudendoplectoceras lahcani gen. et sp. nov.; bed KMO-II, Pragian. 1–3. MB.C.10185. 1, adapical view, not whitened, 41 showing the slightly asymmetrical position of the siphuncle. 2, lateral view. 3, apical view. 4, MB.C. 10186, lateral view. 42 Figs 5–7. Brevicoceras magnum sp. nov., MB.C.9632, holotype; bed PI, early O. costatus conodont Biozone, middle Eifelian. 5, lateral 43 view of cast of body chamber showing longitudinal impressions of muscle scars. 6, adoral view, showing shape of aperture. 7, 44 lateral view of body chamber. 45 Figs 8, 11. Jovellania cheirae sp. nov, MB.C.9603, holotype; bed OJ-II, Lochkovian. 8, ventral view of cast of adapical part of body 46 chamber and phragmocone. 11, adapical view. 47 Figs 9–10, 14. Cerovoceras fatimi gen. et sp. nov., MB.C.9623, holotype; bed PI, early O. costatus conodont Biozone, middle Eifelian. 9, 48 adoral view of body chamber, showing adult aperture and shape of the dorsal horn. 10, lateral view of complete body chamber, 49 position of siphuncle at left side. 14, detail of angular impression between dorsal horn and aperture, adoral view with dorsal side 50 up; scale bar represents 10 mm. 51 Figs 12–13. Cerovoceras brevidomus gen. et sp. nov., MB.C.9620, holotype; bed PI, early O. costatus conodont Biozone, middle Eifelian. 52 12, adoral view of body chamber, showing adult aperture and shape of the dorsal horn. 13, lateral view of complete body 53 chamber, position of siphuncle at left side. 54 All specimens from the Filon Douze section and ·1 except where indicated by scale bar. PLATE 1

1 2 3 4 5 6 7 8 9 1 2 4 10 3 11 12 13 14 15 16 17 18 19 5 20 21 22 23 24 25 26 27 28 6 7 29 30 31 8 32 33 34 35 36 37 38 39 9 40 41 10 11 42 43 44 45 46 47 48 49 50 51 52 53 12 13 14 54 KRO¨ GER, nautiloids 26 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Diagnosis. Cerovoceras with adult size of c. 40 mm in smooth; length of mature body chamber c. 39 mm; aper- 2 conch height and compressed cross-section; ratio of ture broadly rounded-triangular with flattened side on 3 conch width to height 0.9; shell surface smooth; length of antisiphuncular side of conch, with height of c. 22 mm 4 mature body chamber c. 30 mm; aperture rounded-trian- and width 34 mm; broadened subtriangular projection of 5 gular, height c. 24 mm, width 27 mm; antisiphuncular body chamber on antisiphuncular side 20 mm adoral of 6 side of aperture flattened; conspicuous subtriangular pro- last septum; adjacent, contracted part of body chamber 7 jection of body chamber on antisiphuncular side 17 mm about 10 mm long; septa slightly oblique, sloping adap- 8 adoral of last septum; projection forms triangular arc ically on prosiphuncular side. 9 directed towards antisiphuncular side, with central subtri- 10 angular depression; septa oblique, sloping adapically on Description. Holotype is fragment of body chamber and parts of 11 prosiphuncular side; siphuncle close to conch margin, latest chamber of phragmocone. Conch height at base of body 12 compressed ovate in cross-section, with diameter of septal chamber 48 mm, conch width c. 46 mm. Body chamber length 13 perforation 0.2 of conch cross-section. from latest septum to peristome c. 39 mm. Maximum gibbosity of 14 body chamber 20 mm occurs adoral of base of body chamber. At this position on antisiphuncular side conch projection occurs and 15 Description. Holotype is fragment of complete body chamber and just adoral of projection, body chamber constricted forming two latest chambers of phragmocone. Conch height at base of 16 broadened, rounded, triangular apertural opening 21 mm in body chamber 35 mm, conch width c. 33 mm. Body chamber 17 height, spanning prosiphuncular part of body chamber height. length from latest septum to peristome c. 30 mm; maximum gib- 18 Horn-like projection forms broadened rounded triangle with bosity of body chamber occurs 17 mm adoral of base. Here on an- 19 slight depression that opens towards prosiphuncular side. Length tisiphuncular side, conch projection occurs and body chamber 20 of contracted part of body chamber 12 mm. Septal distance constricted just adoral of projection forming rounded-triangular between last two septa 6 mm. Septal curvature shallow concave 21 apertural opening with height of 27 mm, spanning prosiphuncular with deepest point between growth axis and prosiphuncular conch 22 part of body chamber height. Horn-like projection forms rounded margin. Septa oblique, slope towards the apex on prosiphuncular 23 triangle with depression that opens towards prosiphuncular side side. Sutures nearly straight, form faint lateral lobe. Siphuncle 24 (Pl. 1, figs 10, 14). Length of contracted part of body chamber position and shape of septal perforation not visible on specimen. 25 10 mm. Shell thickness close to peristome 1.1 mm. Shell smooth. 26 Septal distance of last two chambers 4 mm. Septal curvature shal- Remarks. Cerovoceras brevidomus differs from C. fatimi in 27 low concave with deepest point of curvature between growth axis having a larger adult size, a shorter body chamber, a 28 and prosiphuncular conch margin. Septa oblique, slope towards slightly depressed cross-section, and a laterally elongated 29 apex on prosiphuncular side. Sutures nearly straight, form faint lateral lobe. Siphuncle positioned c. 3 mm from conch margin and less conspicuous body chamber horn. 30 where conch cross-section 35 mm. Septal perforation compressed 31 ovate, width 5.7 mm, height 7.1 mm. Occurrence. Middle Eifelian; Morocco. 32 33 Remarks. Cerovoceras fatimi differs from C. brevidomus in 34 having a longer body chamber with a circular cross- Family JOVELLANIIDAE Foord, 1888 35 section and a smaller adult size. 36 Genus JOVELLANIA Bayle, in Bayle and Zeiller 1878 37 Occurrence. Early Eifelian; Morocco. 38 Type species. Orthoceratites buchi Verneuil, 1850, from the Siege- 39 nian, Early Devonian of Ne´hou, Manche, France. 40 Cerovoceras brevidomus sp. nov. 41 Plate 1, figures 12–13; Text-figure 12D–F Diagnosis. Straight or slightly cyrtoconic, slowly widening 42 conch with faint undulation; cross-section nearly circular 43 Derivation of name. Latin, breve, short, and domus, house, refer- or slightly depressed with flattened ventrolateral sides 44 ring to the short body chamber of the species. causing slightly angular prosiphuncular side; sutures 45 directly transverse; septa spaced very closely; siphuncle 46 Holotype. MB.C.9620 (Pl. 1, figs 12–13). positioned between centre and conch margin on convex 47 side of growth axis, closer to conch margin than to 48 Type locality and horizon. Filon Douze section, bed PI, early O. growth axis; siphuncular segments expanded within 49 costatus conodont Biozone, middle Eifelian. chambers; endosiphuncular deposits consist of longitudi- 50 nal lamellae. 51 Other material. Known only from the holotype. 52 Remarks. The diagnosis above is a synthesis of generic Diagnosis. Cerovoceras with adult size of c. 51 mm in 53 diagnoses provided by Foerste (1926, p. 306) and Zhu- 54 conch height; slightly depressed cross-section; shell surface 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 27

1 ravleva (1974, p. 44). No information on the septal neck diameter 40 mm), septal distance 3.1 mm and septal perforation 2 shape was given previously. Serpagli and Gnoli (1977, p. 2.5 mm from conch margin. In this specimen connecting ring is 3 95) described cyrtochoanitic septal necks in Jovellania, preserved, showing siphuncular expansion between septa of c. 4 whereas in the specimens from Filon Douze they are 1 mm. Septal necks recumbent; endosiphuncular deposits com- 5 recumbent. However, because no information on the posed of longitudinal lamellae. 6 intra-generic variability of this character is known, the Remarks. This species differs from J. buchi in having a 7 diagnostic value of the septal neck remains unclear. nearly smooth shell with only very faint undulation and 8 lower expansion rate; it differs from all other species of 9 Occurrence. Lochkovian?; France, Germany, Morocco and Tibet. the genus in having a ratio of conch height to width of 10 0.9–1, and a nearly smooth shell. 11 12 Jovellania cheirae sp. nov. 13 Plate 1, figures 8, 11; Plate 2, figures 1, 3–4; Plate 3, 14 figures 1–4 Genus BOHEMOJOVELLANIA Manda, 2001 15 Type species. Bohemojovellania bouskai Manda, 2001, from the 16 Derivation of name. In honour of Cheira, wife of Filon Douze Praha Formation, Pragian, Czech Republic. 17 miner Lahcan Caraoui. 18 Diagnosis (after Manda 2001, p. 274). Cyrtoconic jovella- 19 Holotype. MB.C.9603 (Pl. 3, figs 1–3). nids with smooth, sinistral, bilaterally asymmetric conch; 20 siphuncle on convex side of conch curvature; cross-sec- 21 Type locality and horizon. Filon Douze section, bed OJ-II, Loch- kovian. tion elliptically depressed; c. 10 septa per length similar to 22 conch width; septa moderately concave, sinistrally oblique 23 Other material. 8 fragments, MB.C.9604–9611, 9621, from bed to horizontal axis, with maximum depth of curvature 24 OJ-I, Lochkovian. between dorsoventral axis and convex conch margin; sip- 25 huncle shifted off dorsoventral axis; siphuncular segments 26 Diagnosis. Jovellania with slightly cyrtoconic, slowly one-seventh of conch width in diameter. 27 enlarging conchs; shell surface smooth, only faintly undu- 28 lating; cross-section slightly depressed with flattened ven- Remarks. The otherwise similar Anonymoceras Zhuravl- 29 trolateral sides forming slightly angulate prosiphuncular eva, 1974 differs in having a bilaterally symmetrical 30 side; conch slightly bilaterally asymmetric; sutures form conch. 31 shallow lateral saddles and shallow slightly angular lobe 32 on prosiphuncular side; nine septa in length similar to Occurrence. Lochkovian–Pragian; Czech Republic and Morocco. 33 conch diameter; siphuncle close to conch margin; septal 34 necks recumbent; septal perforation elongate oval in 35 cross-section. Bohemojovellania bouskai Manda, 2001 36 Plate 3, figure 9 37 Description. Conch surface smooth with faint undulations, 38 nearly straight conch in adult growth stages but slightly cyrto- *2001 Bohemojovellania bouskai Manda, pp. 275, 280, 39 conic in juvenile stages (Pl. 3, fig. 4). One adult specimen pl. 1, figs 13–15, text-fig. 6. 40 (MB.C.9621) is known, a fragment of parts of phragmocone and 41 body chamber. Body chamber 59 mm long, 51 mm wide, nearly Material. 2 fragments, MB.C.9616–17, from bed OJ-I, Lochko- 42 tubular shape, faint longitudinal striae at base. Most adoral vian, Filon Douze section. 43 chambers of specimen crowded. Holotype 56 mm long, 35 mm 44 (smallest)–41 mm (largest) in diameter, nearly circular in cross- Diagnosis (after Manda 2001, p. 275). Slightly cyrtoconic 45 section. Ventrolateral sides of conch slightly elongate giving Bohemojovellania with depressed elliptical cross-section, cross-section slightly trapezoidal shape. Entire cross-section a lit- 46 ratio of conch height to width 0.8; cross-section depressed tle bilaterally asymmetrical (Pl. 3, fig. 3). Septal perforation 47 slightly off bilateral axis. Fragments show some variation in rounded trapezoidal with left side of conch slightly more 48 shape of cross-section. Ratio of conch height to width 0.9–1. rounded at position of siphuncular perforation, which is 49 Septal distance in holotype varies between 3.2 and 4.6 mm. close to margin on convex side of growth axis, slightly 50 Sutures describe wide saddle on lateral sides and narrower lobe shifted from dorsoventral axis to left; septa oblique, 51 on prosiphuncular side. Septal perforation 2 mm from conch slightly sloping (8 degrees) in adoral direction on concave 52 margin; conch ovate with height 7.2 mm and width 4.9 mm at side of curvature of growth axis and on right side; septal 53 most adoral septum of holotype (0.18 of conch diameter). In curvature shallow with deepest point of curvature at mid- 54 specimen MB.C.9604, height of siphuncle 5.8 mm (at conch 28 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 length between cross-section centre of gravity and posi- flattened, ventrolateral conch sides and slightly angulate 2 tion of siphuncle; sutures form shallow, wide saddles half- prosiphuncular conch side; cross-section slightly bilater- 3 way between dorsoventral axis and right conch margin at ally asymmetrical with siphuncle slightly shifted off axis 4 convex and concave side of growth axis; ten septa per of symmetry axis; sutures slightly oblique, sloping adoral- 5 length similar to conch height; septal perforation circular ly on prosiphuncular side; septa have strong curvature; 6 in cross-section and c. 0.8 of conch diameter. eight septa per length similar to conch height; siphuncle 7 close to conch margin; septal perforation circular in 8 Description. Conch smooth, very slightly cyrtoconic. MB.C.9616 cross-section. 9 is 11 mm long, 21 mm wide and 18 mm high, displaying four 10 chambers. MB.C.9617 is 9 mm long, 34 mm wide and 27 mm Description. Conch slightly cyrtoconic, surface smooth with faint 11 high, displaying three chambers. Considering cross-section sub- undulations. Holotype 37 mm long, 29–32 mm wide, 23–26 mm 12 divided into 360 degrees, axis of shell curvature along 0–180 high; cross-section broadly elliptical with flattened antisiphuncu- degrees (= dorsoventral axis), with position 0 degrees directed to 13 lar side. Septal perforation shifted slightly off the axis of symme- concave side of curvature of growth axis (=dorsal). Siphuncle in 14 try. Ratio of conch height to width 0.76–0.81, and in some both fragments is close to conch margin at 190 degrees. Septa specimens, antisiphuncular side less flattened than in holotype, 15 slightly oblique along right-left axis of 90–270 degrees sloping in making cross-section nearly perfectly elliptical. Septal distance of 16 apical direction towards left side. Deepest point of septal curva- holotype varies between 1.7 and 3.0 mm. Sutures oblique 17 ture close to centre of gravity of cross-section. Sutures form towards growth axis, sloping towards the aperture on prosiphun- 18 wide saddles half-way between dorsoventral axis and right conch cular side (Pl. 3, fig. 5), describing wide saddle on prosiphuncu- 19 margin. Septal perforation circular, 1.3 mm wide in MB.C.9617, lar side and wide lobe on antisiphuncular side. Septa strongly 20 2.6 mm in MB.C.9616. concave with deepest point of curvature half-way between centre 21 and margin of antisiphuncular side. Septal perforation marginal 22 Occurrence. Lochkovian; Morocco. on concave side of growth axis, circular, diameter 2.6 mm in 23 holotype. Diameter of septal perforation in holotype 0.11 of 24 conch height. Septal necks recumbent and endosiphuncular 25 Bohemojovellania adraei sp. nov. deposits composed of longitudinal lamellae (Pl. 2, fig. 7). 26 Plate 2, figures 2, 7; Plate 3, figures 5–8 Remarks. This species differs from all other species of Bo- 27 hemojovellania in having an only slightly asymmetrical 28 Derivation of name. In honour of my Moroccan friend Adrae. conch. Anonymoceras acceptatum Zhuravleva, 2000, differs 29 Holotype. MB.C.9597 (Pl. 3, figs 5–8). in having a less angular venter in cross-section and a 30 symmetrical conch. 31 Type locality and horizon. Filon Douze section, bed OJ-I, Loch- 32 kovian. 33 Bohemojovellania obliquum sp. nov. 34 Other material. 4 fragments, MB.C.9598–9601, from the type Plate 3, figures 10–12 35 locality and horizon. 36 Derivation of name. Latin, obliquus, oblique. 37 Diagnosis. Bohemojovellania with depressed elliptical 38 cross-section, ratio of conch height to width 0.8; elongate, Holotype. MB.C.9636 (Pl. 3, figs 10–12). 39 40 41 42 EXPLANATION OF PLATE 2 43 Median sections of Oncocerida from the Filon Douze section. 44 Figs 1, 3–4. Jovellania cheirae sp. nov., MB.C.9604; bed OJ-I, Lochkovian. 1, entire fragment. 3, detail showing conspicuous shape of 45 connecting ring, recumbent septal necks and lamellar endosiphuncular deposits. 4, detail showing septal neck. 46 Figs 2, 7. Bohemojovellania adraei sp. nov., MB.C.9601; bed OJ-I, Lochkovian. 2, entire specimen. 7, detail showing conspicuous shape 47 of connecting ring, cyrtochoanitic septal necks and lamellar endosiphuncular deposits. 48 Figs 5, 8. Ankyloceras sp., MB.C.9626; bed OSP-II, Prˇı´dolı´. 5, entire fragment. 8, detail showing conspicuous shape of connecting ring, 49 note the asymmetric shape of septal necks and annular endosiphuncular deposits. 50 Figs 6, 9. Ventrobalashovia zhuravlevai gen. et sp. nov., MB.C.9637, fragment of holotype; bed KMO-III, Pragian. 6, entire fragment. 9, 51 detail showing slightly expanded siphuncular tube, orthochoanitic septal necks and lamellar endosiphuncular deposits. 52 Figs 10–11. Tafilaltoceras adgoi gen. et sp. nov., MB.C.9634, holotype; bed KMO-I, Pragian. 10, entire specimen. 11, detail showing 53 nearly tubular siphuncular tube, orthochoanitic septal necks and lamellar endosiphuncular deposits. 54 Scale bars represent 1 mm; figures without a scale bar are ·1. PLATE 2 1 2 3 4 5 6 7 8 9 1 10 11 12 13 14 15 34 16 2 17 18 19 20 21 22 23 24 25 26 27 28 29 5 30 31 32 33 6 34 35 36 37 38 7 8 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 9 10 11 KRO¨ GER, Oncocerida 30 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Type locality and horizon. Filon Douze section, bed OJ-I, Loch- axis; cross-section elliptical and more narrowly vaulted on 2 kovian. convex side of growth axis curvature; suture line forms 3 broad lateral lobes; siphuncle marginal on convex side of 4 Other material. 2 fragments, MB.C.9602, 9691, from the type conch growth axis; siphuncle scalariform; siphuncular seg- 5 locality and horizon. ments strongly expanded towards conch margin at adapical 6 part of each segment, strongly expanded towards conch 7 Diagnosis. Slightly cyrtoconic Bohemojovellania with centre at adoral part of each segment, at expanded portions 8 depressed elliptical cross-section, ratio of conch height to touching surface of septa; septal necks loxochoanitic on 9 width 0.8; left side of conch slightly more rounded at posi- side directed towards conch margin, short recumbent on 10 tion of siphuncular perforation, which is close to conch side directed towards growth axis. 11 margin on convex side of conch growth axis, strongly 12 shifted from dorsoventral axis to left; septa oblique, sloping Occurrence. Early Devonian; Japan, Morocco, Novaya Zemlya 13 in adoral direction on concave side of curvature of growth and Russia. 14 axis and on right side; septal curvature shallow, with deepest 15 point of curvature at mid-length between cross-section cen- 16 tre of gravity and position of siphuncle; sutures form shal- Ankyloceras sp. 17 low saddles half-way between dorsoventral axis and right Plate 2, figures 5, 8; Plate 3, figures 13–14 18 conch margin on convex and concave side of growth axis; 19 ten septa per length similar to conch height; septal perfo- Material. 1 specimen, MB.C.9626, from bed OSP-II, Prˇı´dolı´, 20 ration circular in cross-section and c. 0.8 of conch diameter. Filon Douze section. 21 22 Description. Conch smooth, very slightly cyrtoconic with angle Description. Fragment of phragmocone, length c. 72 mm. Only of expansion of 5 degrees. Only fragments of phragmocone convex half of cyrtoconic conch preserved. Cross-section appears 23 known. Holotype 37 mm long, 28–32 mm wide, 22– 29 mm to be circular or slightly depressed with diameter at adoral end 24 high. Considering cross-section subdivided into 360 degrees, axis 28 mm. Siphuncle marginal on convex side of conch curvature. 25 of shell curvature along 0 ⁄ 180 degrees (= dorsoventral axis) and Conch surface smooth with slightly irregular transverse undula- 26 0 degrees directed towards centre of growth curvature (= direc- tions. Septal spacing slightly irregular with septal distances 1.5– 27 tion of concave side of curvature of growth axis). Siphuncle in 2.6 mm. Septal perforation depressed oval, 1.8 mm in cross-sec- 28 holotype 2 mm from conch margin at position of 250 degrees tion. Septal necks cyrtochoanitic on side of siphuncle directed 29 (Pl. 3, fig. 12). Septa oblique along right ⁄ left axis 90–270 towards conch margin, and strongly recumbent on side directed 30 degrees, sloping in apical direction on left side of (Pl. 3, fig. 10). towards conch centre. Siphuncular segments strongly expanded. 31 Deepest point of septal curvature halfway between centre of Connecting ring forms rounded-convex segments that touch ad- 32 gravity of cross-section and position of siphuncle. Sutures form apical surface of septa on side directed towards growth axis of 33 wide saddles half-way between dorsoventral axis and right conch conch and touch adoral septal surface on side directed towards margin. Septal perforation in holotype 2.6 mm wide and circu- conch margin. Endosiphuncular deposits form adapically elon- 34 lar. Septal perforation of MB.C.9691 2 mm from conch margin gated bullettes at position of septal perforation. 35 at 225 degrees, with circular cross-section of 4.5 mm; this speci- 36 men is a fragment with five chambers with septal distance of Remarks. In contrast to the type of the genus, this speci- 37 3.5 mm, conch width 52 mm, conch height 39 mm. men has ventrally directed septal necks that are cyrtocho- 38 anitic, not loxochoanitic. However, as there is no 39 Remarks. This species differs from B. bouskai in having a information of the variability of this character within the 40 more oblique, eccentric siphuncle. genus, I consider the difference small enough to allow 41 assignation to Ankyloceras. Because the single specimen 42 reveals no information on the general conch shape, a spe- 43 Family KAROCERATIDAE Teichert, 1939 cific designation is impossible. The specimen may be con- 44 specific with Ankyloceras sardoum (Serpagli and Gnoli, 45 Genus ANKYLOCERAS Zhuravleva, 1974 1977) but its curvature is stronger; and the segments of 46 the siphuncle are more expanded in the latter. 47 Type species. Cyrtoceras nesnayamiense Foerste, 1925, from the 48 Lower Devonian of Novaya Zemlya, Russia. 49 Genus VENTROBALASHOVIA gen. nov. 50 Diagnosis (after Zhuravleva 1974, p. 67). Cyrtocone karo- 51 ceratids with compressed to slightly depressed cross-sec- Type species. Ventrobalashovia zhuravlevai sp. nov., from the 52 tion, ornamented with faint growth lines displaying distinct Pragian of the Filon Douze section. 53 lobe on convex and sometimes on concave side of growth 54 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 31

1 Derivation of the name. Latin, venter, belly, referring to the margin on convex side of growth axis, and flattened on 2 ventral siphuncle of this genus, which is otherwise similar to concave side of this axis, with height to width ratio of 3 Balashovia Zhuravleva, 1974. 0.8; siphuncle at convex side of conch curvature slightly 4 removed from margin; about eight septa per distance 5 Other species included. Tripleuroceras altajense Zhuravleva, 1979 similar to conch width; septal curvature very shallow; 6 (species combined with Ventrobalashovia below: see ‘List of new siphuncular diameter 0.2 of conch height; siphuncle only combinations’). 7 slightly expanded within chambers; septal necks orthocho- 8 anitic to loxochoanitic, relatively long; endosiphuncular Diagnosis. Slightly cyrtoconic oncocerids with undulating 9 deposits as longitudinal lamellae. shell; cross-section with rounded margin on convex side 10 of growth axis and flattened margin on concave side; sip- 11 Description. Conch slightly cyrtoconic with angle of expansion huncle positioned on convex side of conch curvature, 12 of 7 degrees. Holotype 58 mm long, 34–50 mm wide, 32–40 mm slightly removed from conch margin; c. 8 septa per length 13 high. Conch undulating with distance between two undulations similar to conch width; septal curvature very shallow; sip- 14 11 mm; these slope in adoral direction on prosiphuncular side. huncular diameter 0.2–0.3 of conch height; siphuncle only 15 Cross-section nearly elliptical, flattened on concave side of slightly expanded within chambers; septal necks orthocho- growth axis (Pl. 3, fig. 17). Septa straight with shallow concavity. 16 anitic to loxochoanitic, relatively long; endosiphuncular Sutures form shallow, narrow lobe on prosiphuncular side. 17 deposits as longitudinal lamellae. Septal perforation 5 mm from conch margin on convex side of 18 conch curvature. Septal necks orthochoanitic or loxochoanitic, 19 Remarks. This genus is similar to typical jovellanids in 2.5 mm long. Siphuncular segments only slightly expanded. Dif- 20 the general conch shape. However, Jovellania has cyrto- ference between diameter of septal perforation and maximum 21 diameter of siphuncle 1.8 mm. Endosiphuncular deposits consist choanitic or recumbent septal necks. By contrast, the long 22 of longitudinal lamellae. orthochoanitic to loxochoanitic septal necks of Ventrobal- 23 ashovia are similar to Balashovia Zhuravleva, 1974, which 24 Remarks. This species differs from Tripleuroceras altajiense was assigned to the Tripleuorthoceratidae because it has a 25 Zhuravleva, 1979 in having a wider cross-section, a more siphuncle on the concave side of conch curvature and a 26 eccentric, narrower siphuncle and a higher expansion flattened venter. Ventrobalashovia has a siphuncle on the 27 rate. convex side of shell curvature and a flattened dorsum, 28 and thus differs from genera assigned to both the Jovella- 29 niidae and the Tripleurorthoceratidae. This relationship 30 Family NOTHOCERATIDAE Fischer, 1882 problem can only be solved when the internal characters 31 of Tripleuroceras Hyatt, 1884 are better known and the 32 Genus MUTOBLAKEOCERAS gen. nov. Tripleuroceratidae are revised. 33 34 Type species. Mutoblakeoceras inconstans sp. nov., from the Eif- Occurrence. Pragian–Eifelian; Altai Mountains (Russia) and elian of the Filon Douze section. 35 Morocco. 36 37 Derivation of name. Latin, muto, to change, with reference to 38 the ontogenetically changing cross-section shape of the genus, Ventrobalashovia zhuravlevai sp. nov. which is otherwise similar to Blakeoceras Foerste, 1926. 39 Plate 2, figures 6, 9; Plate 3, figures 15–17 40 Other species included. None. 41 Derivation of name. In honour of F. A. Zhuravleva, Moscow, for 42 her lifelong research on nautiloids. Diagnosis. Slightly cyrtoconic nothoceratids with angle 43 of expansion of 18 degrees; cross-section compressed 44 Holotype. MB.C.9637. adapically, depressed in later growth stages; septa 45 straight, transverse and with shallow concavity; about 46 Type locality and horizon. Filon Douze section, bed KMO-III, eight septa per distance similar to cross-section; septal 47 Pragian. perforations c. 0.1 of conch cross-section; marginal sip- 48 huncle at convex side of shell curvature; siphuncular 49 Other material. Known only from the holotype. segments tubular with thick outer layer of connecting 50 rings, thickest in vicinity of septal perforation, giving 51 Diagnosis. Ventrobalashovia with obliquely undulating impression of concave segments; septal necks subortho- 52 shell; two undulations per distance similar to length of choanitic; Endosiphuncular deposits as continuous lon- 53 two chambers; undulations slope towards aperture on gitudinal lamellae. 54 prosiphuncular side of conch; cross-section with rounded 32 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Remarks. The typical concave appearance of the siphuncu- Derivation of the name. After Tafilalt, with reference to the type 2 lar segments in the type qualifies the genus as a nothocera- locality. 3 tid. This large species differs from all other nothoceratids in 4 having a cross-section that changes during ontogeny from Other species included. None. 5 compressed to depressed. The genus differs from the other- 6 wise similar Blakeoceras in having a less curved conch and a Diagnosis. Gradually expanding cyrtoconic nothoceratids 7 compressed to depressed cross-section. with angle of expansion of 12 degrees; cross-section sub- 8 circular, slightly depressed; septa straight, transverse and 9 Occurrence. Eifelian; Morocco. with shallow concavity; about nine septa per distance 10 similar to cross-section; septal perforations c. 0.16 of 11 conch cross-section; marginal siphuncle at convex side of 12 Mutoblakeoceras inconstans sp. nov. shell curvature; siphuncular diameter c. 0.1 of cross-sec- 13 Plate 4, figures 2–3, 5; Plate 5, figure 1 tion diameter; siphuncular segments tubular with thick 14 outer layer of connecting rings, thickest in vicinity of sep- 15 Derivation of name. Latin, inconstans, inconsistent, with refer- tal perforation, giving impression of concave segments; 16 ence to the ontogenetic change in the cross-section of this septal necks suborthochoanitic; endosiphuncular deposits 17 species. as continuous longitudinal lamellae. 18 19 Type locality and horizon. Filon Douze section, bed F, P. partitus Remarks. Although the ornamentation of Tafilaltoceras is conodont Biozone, early Eifelian. 20 not known in detail because the holotype is heavily over- 21 grown by epizoans, it is apparently smooth and clearly Other material. Known from the holotype only. 22 without undulations. It differs from the otherwise similar 23 Blakeoceras Foerste, 1926, in having a slightly depressed Diagnosis. As for genus, by monotypy. 24 cross-section, from Conostichoceras Foerste, 1926, in hav- 25 ing a gradually widening, more elongate conch, and from Description. Specimen is fragment of very slightly cyrtoconic Turneroceras Foerste, 1926, in lacking a flattened venter. 26 phragmocone 92 mm long; conch width 34–64 mm, height 39– A diagnostic character of the Nothoceratidae is the 27 56 mm. Thus, conch adapically compressed and adorally depressed 28 in cross-section with angle of expansion of c. 18 degrees (Pl. 4, figs ‘concavosiphonate siphuncle’ (Sweet 1964a, p. K305). In 29 2, 5). Siphuncle marginal at convex side of conch curvature. Frag- Tafilaltoceras the siphuncle also appears to be concavos- 30 ment has 11 chambers. Septa slightly oblique, sloping in adoral iphonate. However, the better preserved areas in the type 31 direction on prosiphuncular side. Septal spacing slightly irregular reveal that the siphuncular segments are tubular and the 32 with septal distances between 5 mm (adapically) and 11 mm (ado- apparent vacuosiphonate (=concavosiphonate) shape of 33 rally). Diameter of septal perforation 6.4 mm at adoral end. the siphuncle is an effect of the very conspicuous, thick 34 outer layer of the connecting ring, thickest in the vicinity 35 of the septal perforation (Pl. 2, fig. 11). There is a high 36 Genus TAFILALTOCERAS gen. nov. probability this is also the case in other nothoceratidans. 37 38 Type species. Tafilaltoceras adgoi sp. nov., from the Pragian of Occurrence. Pragian; Morocco. the Filon Douze section. 39 40 41 42 EXPLANATION OF PLATE 3 43 Figs 1–4. Jovellania cheirae sp. nov., MB.C.9603, holotype; bed OJ-I, Lochkovian. 1–3. 1, dorsal view. 2, lateral view. 3, adapical view. 44 4, MB.C.6905 slightly cyrtoconic juvenile conch section. 45 Figs 5–8. Bohemojovellania adraei sp. nov., MB.C.9597, holotype; bed OJ-I, Lochkovian. 5, lateral view. 6, ventral view. 7, dorsal view. 46 8, adapical view; note the slightly asymmetric position of siphuncle. 47 Fig. 9. Bohemojovellania bouskai Manda, 2001, MB.C.9616; bed OJ-I, Lochkovian, adapical view; note the slightly asymmetric position 48 of siphuncle. 49 Figs 10–12. Bohemojovellania obliquum sp. nov., MB.C.9602, holotype; bed OJ-I, Lochkovian. 10, lateral view. 11, dorsal view. 12, 50 adapical view; note the clearly asymmetric position of siphuncle. 51 Figs 13–14. Ankyloceras sp., MB.C.9626, fragment of holotype; bed KMO-I, Pragian. 13, lateral view. 14, adapical view. 52 Figs 15–17. Ventrobalashovia zhuravlevai gen. et sp. nov., MB.C.9637, fragment of holotype; bed KMO-III, Pragian. 15, lateral view. 53 16, ventral view. 17, adapical view. 54 All specimens from the Filon Douze section and ·1. PLATE 3 1 2 3 4 5 6 7 8 9 10 11 4 12 13 14 1 23 15 16 17 18 19 20 21 22 8 23 24 5 67 25 26 27 28 29 30 31 12 32 9 33 13 34 10 11 35 36 37 38 39 40 14 41 42 43 44 45 46 47 48 49 15 16 50 51 52 53 17 54 KRO¨ GER, nautiloids 34 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Tafilaltoceras adgoi sp. nov. Family ONCOCERATIDAE Hyatt, 1884 2 Plate 2, figures 10–11 3 Genus ORTHORIZOCERAS gen. nov. 4 Derivation of name. In honour of Adgo, youngest son of Filon 5 Douze miner Lahcan Caraoui. Type species. Orthorizoceras desertum sp. nov., from the upper 6 Prˇı´dolı´ of the Filon Douze section. 7 Holotype. MB.C.9634 (Pl. 2, figs 10–11). 8 Derivation of the name. Greek, orthos, straight, referring to the straight conch. 9 Type locality and horizon. Filon Douze section, bed KMO-I, Pragian. 10 Other species included. Metarizoceras sinkovense Balashov, in Bal- 11 Other material. Known only from the holotype. ashov and Kiselev 1968 (species combined with Orthorizoceras 12 below: see ‘List of new combinations’). 13 Diagnosis. As for the genus. 14 Diagnosis. Straight, rapidly widening, breviconic oncocer- 15 Description. Fragment of phragmocone 77 mm long, conch ids with slightly compressed to slightly depressed cross- 16 height 18–34 mm, adoral width 37. Cross-section slightly section; about five septa at distance similar to conch 17 depressed. Conch surface not known but no undulations or cross-section; septa slightly oblique, sloping towards apex 18 evidence for ornamentation visible in cross-section. Septal dis- on prosiphuncular side; sutures form shallow lateral lobe; 19 tance at adoral end of specimen 4.5 mm. Septal curvature siphuncle close to conch margin; siphuncular segments 20 shallow concave. Siphuncle positioned at margin on convex expanded within chambers; septal necks cyrtochoanitic; 21 side of conch curvature. Septal perforation at most adoral endosiphuncular and cameral deposits not known. 22 septum 5.5 mm, where thickness of siphuncle is 4.3 mm. Siphuncular segments nearly tubular. Connecting ring dis- 23 Remarks. Orthorizoceras is similar to Rizoceras and Metari- plays thick outer layer that expands over the adapical surfaces 24 zoceras Foerste, 1930, but differs in having a straight conch of suborthochoanitic septal necks, forming wedge at adapical 25 surface of septal neck and at adoral surface of septal perfora- that has its largest diameter adapical of the base of the body 26 tion. chamber. The conch of Rizoceras gradually widens, and that 27 of Metarizoceras has its largest diameter at the base of the 28 body chamber. The septal spacing of Orthorizoceras is also 29 Indet. Nothoceratidae sp. A. much greater than that of these two genera. 30 Plate 4, figure 1; Plate 5, figure 2 31 Occurrence. Prˇı´dolı´; Ukraine and Morocco. 32 Material. 1 specimen, MB.C.9635, from bed PI, early 33 O. costatus conodont Biozone, middle Eifelian; Filon Douze 34 section. Orthorizoceras desertum sp. nov. 35 Plate 4, figure 4; Plate 9, figure 8 36 Description. Specimen is fragment of phragmocone 83 mm 37 long with smooth shell. Cross-section slightly depressed; maxi- Derivation of name. Latin, deserta, desert, referring to the type 38 mum conch width 67 mm, conch height 71 mm. Angle of locality, which is at the northern margin of the Sahara. 39 expansion c. 21 degrees. Siphuncle marginal at convex side of 40 conch curvature. Twelve chambers preserved. Septal spacing Holotype. MB.C.9633 (Pl. 4, fig. 4; Pl. 9, fig. 8). 41 slightly irregular with septal distances of c. 5 mm. Septal perforation has diameter of 10 mm at adoral end. Septal Type locality and horizon. Filon Douze section, bed OSP-II, 42 necks orthochoanitic. Siphuncular segments appear concave. Prˇı´dolı´an. 43 Endosiphuncular deposits occur adapically as longitudinal 44 lamellae. Other material. Known only from the holotype. 45 46 Remarks. This specimen differs from Mutoblakeoceras in- Diagnosis. Orthorizoceras with angle of expansion of c. 20 47 constans in having a larger angle of expansion and a degrees; maximum cross-section diameter adapical of body 48 depressed cross-section. A depressed cyrtoconic phragmo- chamber c. 30 mm; cross-section slightly depressed, height 49 cone is characteristic of Turnoceras and Constichoceras, to width ratio 0.9; septa slightly oblique, sloping towards 50 which differ mainly in the shape of the adult body chamber. apex on prosiphuncular side; sutures form shallow lateral 51 Because the body chamber is not preserved in the Filon lobe; siphuncle close to conch margin; siphuncular segments 52 Douze fragment a generic or specific determination cannot expanded within chambers; septal necks cyrtochoanitic; en- 53 be made. dosiphuncular and cameral deposits not known. 54 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 35

1 Description. Fragment of phragmocone 36 mm long, conch 14– Description. Specimen displays eight chambers of intermediate 2 29 mm high, width adapically 16 mm. Maximum diameter of growth stages of conch belonging to most adoral part of 3 cross-section at position of second youngest chamber. Outer phragmocone. Additionally cast of outer shell of innermost 4 shell not preserved. Septal crowding of most adoral septa indi- whorls is preserved. Diameter at position of youngest preserved 5 cates maturity of specimen. Septal distance at adoral end of septum 62 mm. Maximum whorl height of preserved chambers specimen 3 mm, at apical end 4 mm. Maximum septal distance c. 32 mm, minimum preserved whorl height c. 25 mm. Length 6 5 mm. Septal curvature shallowly concave. Septal perforation of curvature of conch part 52 mm. Septa at distances of 5– 7 positioned 1.5 mm from conch margin at most apical septum, c. 9 mm. Most adoral four preserved chambers crowded, giving 8 0.1 of cross-section. Siphuncular segments expanded within evidence for maturity of specimen. Septa deeply concave, oblique 9 chambers. Siphuncular diameter 3 mm at apical end of speci- towards radial axis, sloping towards apex on convex conch side. 10 men. Dorsum broad, with straight margin in adoral part, maximum 11 width 46 mm, convex in adapical part. Lateral sides rounded, 12 Remarks. This species differs from Metarizoceras sinko- ornamented with faint, irregularly spaced, transverse undulations 13 vense Balashov, in Balashov and Kiselev 1968 in having a and lirae that form conspicuous lobe at venter (Pl. 4, fig. 13). 14 smaller adult size and wider septal spacing. Convex side of shell not preserved. Septal perforation not visible, 15 but it cannot be central or between centre and dorsum. 16 Remarks. This specimen shows diagnostic features of Cen- 17 Order NAUTILIDA Agassiz, 1847 troceras such as the general shell shape, shape of septa 18 Family CENTROCERATIDAE Hyatt, 1900 19 and sutures, and ornamentation. However, the conch venter is only poorly preserved. Because this character is 20 Genus CENTROCERAS Hyatt, 1884 21 important for assignment to a species, such a course of 22 Type species. Goniatites marcellensis Vanuxem, 1842, from the action for this single fragment is impossible, and the exact 23 Cherry Valley limestone, Eifelian, of central New York, USA. position of the siphuncle is unknown. 24 25 Diagnosis (after Kummel et al. 1964, p. K434). Tarphy- 26 ceraconic nautiloid consisting of few, rapidly expanding Order ACTINOCERIDA Teichert, 1933 27 volutions; umbilical window wide; slightly impressed zone Family ORMOCERATIDAE Saemann, 1852 28 near base of mature living chamber; whorl sections tetrago- 29 nal, with sharp ventral and umbilical shoulders; dorsum Genus ORMOCERAS Stokes, 1840 30 broad, convex in young, nearly straight in mature, por- 31 tions; lateral areas oblique, convergent towards narrow, Type species. Orthoceras bayfieldi Stokes, 1838, from the Niaga- ran (Wenlock) of Drummond Island, Lake Huron, Canada. 32 scarcely convex venter; whorls compressed; sutures form 33 shallow ventral lobe and broad lateral lobe with subacute Diagnosis (after Teichert 1964, p. K211). Conch straight 34 saddles on shoulders, dorsal portion nearly transverse with nearly circular cross-section; siphuncle subcentral with 35 except in mature portion where broad shallow lobe occurs; almost globular segments; septal necks cyrtochoanitic with 36 siphuncle tubular, positioned near venter; living chamber short brims; annulosiphuncular deposits with simple endo- 37 comprises half a volution in length; ornamented with alter- siphuncular canal system and few radial canals; cameral 38 nating striae and lirae which are more or less fasciculate; depositscommon. 39 ventral shoulders of early volutions with small nodes. 40 Occurrence. Middle Ordovician–Early Devonian; world-wide. 41 Remarks. The record of Centroceras sp. from the Emsian 42 of Filon Douze is the oldest of the genus and of the Nau- 43 tilida in general. Ormoceras sp. 44 Plate 5, figure 3; Text-figure 13B 45 Occurrence. Zlı´chovian–Givetian; Armenia, Germany, Morocco and North America. 46 Material. 1 specimen, MB.C.9639, from bed KMO-I, Pragian, 47 Filon Douze section. 48 Centroceras sp. 49 Description. Fragment of six chambers of phragmocone, straight, Plate 4, figures 11–13 50 length 29 mm, cross-section diameter adorally c. 18 mm. 51 Because of fragmentary character of specimen, angle of expan- 52 Material. 1 specimen, MB.C.9628, from the top of bed KMO- sion cannot be determined. Minimum distance between septa ´ 53 IV, Zlıchovian, Emsian, Filon Douze section. 4.5 mm (at adoral end of fragment), maximum distance 5.2. 54 36 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Septal concavity shallow with 2.8 mm curvature depth at adapi- Holotype. MB.C.9630 (Pl. 5, figs 7–8; Pl. 16, fig. 8; Text- 2 cal septum. Siphuncle eccentric. Septal perforation diameter fig. 13A). 3 3.1 mm where cross-section diameter is 17 mm. Diameter of 4 siphuncle c. 5 mm. Siphuncular segments subglobular, widely Type locality and horizon. Filon Douze section, Deiroceras Lime- 5 expanded within chambers with height to width ratio of 0.8. stone, Zlı´chovian, Emsian. Septal necks cyrtochoanitic. Brims of septal necks display con- 6 spicuous sharp bend at distal one-third of necks. Annulosiphun- 7 Other material. 3 specimens, MB.C.9640, 9768.1–2, from the cular deposits thicker on ventral side of siphuncle. Cameral type locality and horizon. 8 deposits occur on prosiphuncular side of conch. 9 Diagnosis. Deiroceras with angle of expansion of 2 10 Remarks. The fragment is assigned to Ormoceras because degrees, ornamented with fine transverse lirae; conch 11 of the presence of cyrtochoanitic septal necks that display cross-section nearly circular; septal spacing wide, c. 2 12 a conspicuous sharp bend at their brims. The widely septa per distance similar to conch diameter; diameter of 13 expanded siphuncular segments are subglobular in longi- septal perforation c. 0.27 of conch cross-section; septal 14 tudinal section. However, the fragmentary nature of the necks suborthochoanitic; siphuncle subcentral; siphuncu- 15 single specimen does not allow a specific determination. lar segments elongate, ovate; annulosiphonate deposits 16 with simple, straight radial canals closer to adapical sur- 17 face of each septum than to adoral surface and perpendic- 18 Genus DEIROCERAS Hyatt, 1884 ular or slightly oblique to narrow central canal; with 19 episeptal and hyposeptal deposits. 20 Type species. Orthoceras python Billings, 1857, from the Cobourg 21 Beds, Ottawa Formation, Caradoc, late Ordovician, of Ottawa, Description. Conch with very low angle of expansion (c.2 22 Ontario, Canada. degrees). Shell surface ornamented with fine transverse lirae; 23 5about ten lirae occur within distance of 2 mm (Pl. 16, fig. 8). 24 Diagnosis (after Teichert 1964, p. K212). Slender, gradu- Septal distance in holotype 19 mm at conch diameter of 41 mm, 25 ally expanding, orthoconic longicones; conch cross-sec- in MB.C.9640, 14 mm at conch diameter of 30 mm. Septa have 26 tion nearly circular; septal spacing wide; septal necks deep curvature and are slightly conical in shape. Septal perfora- 27 suborthochoanitic; siphuncle between conch margin and tion subcentral with diameter of 11 mm in holotype (0.27 of 28 centre; siphuncular segments longer than wide, ovate; conch diameter), 6.5 mm in MB.C.9640 (0.22 of conch diame- 29 annulosiphonate deposits with simple, straight radial ter). Siphuncular segments elongate-ovate. Diameter of siphun- 30 canals perpendicular or slightly oblique to narrow central cular segment at mid-length of holotype 17.7 mm (0.43 of 31 canal; with episeptal and hyposeptal deposits. diameter), in MB.C.9640 11.8 mm (0.39 of conch diameter). En- dosiphuncular deposits consist of massive annuli, slightly elon- 32 gated in adoral direction. Contact surface between two Occurrence. Middle Ordovician–Early Devonian; world-wide. 33 successive annuli slightly oblique towards growth axis and cen- 34 tral canal. In holotype, adapical contact surface of endosiphun- 35 cular annuli occurs 7.4 mm from septal perforation, adoral 36 Deiroceras hollardi sp. nov. contact surface 12 mm from it. Central canal appears to be off- 37 Plate 5, figures 7–8; Plate 16, figure 8; Text-figure 13A centre of siphuncle. However, in MB.C.9640 median section dis- 38 plays centrally positioned central canal. On prosiphonal side of 39 Derivation of name. In honour of Henri Hollard who was a pio- conch episeptal and hyposeptal deposits occur. 40 neering researcher on the geology and stratigraphy of Morocco. 41 42 43 EXPLANATION OF PLATE 4 44 Fig. 1. Indet. Nothoceratidae sp. A., MB.C.9635; bed PI, early O. costatus conodont Biozone, middle Eifelian; dorsal view. 45 Figs 2–3, 5. Mutoblakeoceras inconstans gen. et sp. nov., MB.C.9584; bed PI, early O. costatus conodont Biozone, middle Eifelian. 2, 46 adapical view. 3, lateral view. 5, adoral view; note the depressed adoral cross-section and the compressed adapical cross-section. 47 Fig. 4. Orthorizoceras desertum gen. et sp. nov., MB.C.9633, holotype; bed OSP-II, Prˇı´dolı´; lateral view. 48 Figs 6–7. Subormoceras sp., MB.C.9674; bed OSP-I, Prˇı´dolı´. 6, lateral view. 7, dapical view; note the clear asymmetric position of 49 siphuncle. 50 43 Figs 8–9. Orthocycloceras? fluminense (Meneghini 1857), MB.C.9612; bed OSP-I, Prˇı´dolı´. 8, ventral view. 9, lateral view. 51 Fig. 10. Subormoceras rissaniense gen. et sp. nov., MB.C.9622; bed F, P. partitus conodont Biozone, Eifelian, lateral view. 52 Figs 11–13. Centroceras sp., MB.C.9623; bed KMO-IV, Zlı´chovian, Emsian. 11, lateral view. 12, adoral view. 13, detail of lateral view 53 showing conch ornamentation. Scale bar represents 10 mm. 54 All specimens from the Filon Douze section and ·1 except where indicated by scale bar. PLATE 4 1 2 3 4 5 6 7 8 9 10 11 12 2 13 14 1 15 16 17 18 19 20 21 22 23 3 24 4 25 26 27 28 29 5 30 31 32 33 34 35 36 7 37 6 38 39 8 9 40 41 42 43 44 45 46 47 48 49 50 51 52 53 10 11 12 13 54 KRO¨ GER, nautiloids 38 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 lar segments. It is possibly conspecific with Orthoceras beyri- 2 6chi Kayser, 1878 from the Devonian of the German Harz 3 Mountains, which is similar in general conch shape and in 4 the shape of the siphuncle. However, the single illustration 5 of this species (pl. 10, fig. 5) does not show the shape of sep- 6 tal necks and internal details of the siphuncle and the type 7 specimen could not be located for comparison. 8 9 10 Genus METARMENOCERAS Flower, 1940 11 12 Type species. Metarmenoceras bilaterale Flower, 1940, from the A 13 Dalhousie beds, Early Devonian, of Gaspe´, Quebec, Canada. 14 15 Diagnosis (after Flower 1940, p. 445). Slightly depressed 16 orthocones with straight, transverse sutures; siphuncle eccen- 17 tric with broadly expanded nummuloidal segments twice as 18 wide as long; septal necks recumbent; expanded segments 19 touch adoral and adapical surface of septa; radial canal com- 20 pressed, touching inner surface of connecting ring at side of 21 siphuncle, directed towards conch margin; radial canals bilat- 22 erally symmetric; episeptal and hyposeptal deposits. 23 24 Occurrence. Late Silurian–Early Devonian; Canada, Japan, Sardi- 25 nia and Ukraine. B 26 27 28 Metarmenoceras fatimae sp. nov. 29 Plate 5, figures 4–5; Text-figure 13C 30 31 Derivation of name. In honour of Fatima, daughter of Filon Douze miner Lahcan Caraoi. 32 33 Holotype. MB.C.9642 (Pl. 5, figs 4–5; Text-fig. 13C). 34 35 Type locality and horizon. Filon Douze section, Erbenoceras 36 Limestone, Zlı´chovian, Emsian. 37 38 Other material. 2 specimens, MB.C.9641, 9570, from the type 39 locality and horizon; 2 specimens, MB.C.9643–44, from the 40 Deiroceras Limestone at the type locality, Zlı´chovian. 41 cameral deposits C 42 endosiphuncular deposits Diagnosis. Metarmenoceras with nearly circular cross- 43 TEXT-FIG. 13. Camera lucida drawings of median sections of section and smooth conch surface; siphuncle subcentral; 44 Early Devonian Ormoceratidae from Filon Douze. A, Deiroceras siphuncular segments subquadratic in median section, 45 hollardi sp. nov.; MB.C.9630, Deiroceras Limestone, Zlı´chovian. nearly as long as wide and strongly expanded within cham- 46 B, Ormoceras sp.; MB.C.9639, bed KMO-I, Pragian. C, bers, c. 0.2 of conch cross-section in diameter; diameter of 47 Metarmenoceras fatimae sp. nov.; MB.C.9642, Erbenoceras septal perforation half of diameter of siphuncular segments. 48 Limestone, Zlı´chovian. Scale bar represents 10 mm. 49 Description. Three fragments have angle of expansion of 7 (holo- 50 Remarks. Deiroceras hollardi differs from all other species of type), 9 (MB.C.9644), and 10 (MB.C.9643) degrees. Conch very 51 Deiroceras in combining a very low angle of expansion with slightly curved with siphuncle on convex side of growth axis. 52 wide chamber distance and a fine transverse ornamentation; Holotype is fragment of phragmocone 70 mm long, minimum 53 it differs from the Silurian D. amatum Heritsch, 1931, in cross-section diameter 26 mm. Second specimen (MB.C.9644) 65 mm long, minimum cross-section diameter 32 mm. 54 having less bent septal necks and more elongated siphuncu- 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 39

1 MB.C.9643 134 mm long, cross-section diameter 38–62 mm. No Derivation of name. From a contraction of Geisonoceras Hyatt, 2 parts of body chamber preserved in specimens. Conch cross-sec- 1884 and Dolorthoceras Miller, 1931. Geidoloceras is superficially 3 tion nearly circular. In holotype seven chambers occur within similar to the former but internally similar to the latter. 4 length of 42 mm; in second specimen ten chambers occur within 5 length of 65 mm. Septal necks recumbent, touching adapical sur- Other species included. None. faces of septa (Pl. 5, fig. 4). Septal perforations positioned subcen- 6 trally with cross-section diameter 2.8–2.9 mm in holotype. Diagnosis. Straight or very slightly cyrtoconic pseudortho- 7 Siphuncular segments have diameter of 5.6–6.4 mm in holotype 8 ceridans; ornamented with rounded transverse ridges with and a subquadratic outline in median section. Connecting ring narrow interspaces; conch cross-section nearly circular; c. 5 9 touches septal surfaces on adapical and adoral sides. Strong annu- septa per distance similar to conch diameter; septal necks 10 lar endosiphuncular deposits occur that have wide, irregularly 11 shaped central canal. Deposits on dorsal side of siphuncle more short cyrtocoanitic; siphuncle subcentral; siphuncular seg- 12 massive and irregularly shaped. Hyposeptal and episeptal deposits ments expanded within chambers, elongate, ovate with lar- 13 occur on prosiphuncular side of conch. ger expansion at adoral third of each segment; parietal 14 endosiphuncular deposits strongly elongated adapically. 15 Remarks. This species differs from other species of Metar- 16 menoceras in having a comparatively narrow siphuncle Remarks. Geidoloceras differs from Dolorthoceras in 17 with subquadrate segments. having a transversely ornamented shell. Geisonoceroides 18 Flower, 1939, differs in having concave interspaces 19 between the transverse ridges that are similar in width to 20 Order PSEUDORTHOCERIDA Barskov, 1963 that of the ridges. Compared to Geisonoceroides, the inter- 21 spaces of the ridges and interspaces of Geidoloceras are 22 7Remarks. Kro¨ger (2006) and Kro¨ger and Isakar (2006) very closely spaced. Fukujiceras Niko, 1996, which is a 23 pointed out that Orthocerida and Pseudorthocerida are sis- transversely annulated pseudorthocerid with suborthocho- 24 ter groups. They stated that Pseudorthocerida differ from anitic septal necks, differs from Geidoloceras in having en- 25 the Orthocerida in having a conical apex with a cicatrix and dosiphuncular deposits that originate in the mid-length 26 cyrtochoanitic septal necks, a conclusion drawn from the of segments. Subdoloceras gen. nov. differs in having a 27 observation that all cyrtochoanitic orthocones display these finer ornamentation and suborthochoanitic septal necks. 28 characters. However several morphologies exist that are 29 intermediate between typical orthocerids and pseudortho- Occurrence. Pragian; Morocco. 30 cerids, having achoanitic or suborthochoanitic septal necks. 31 The conical, cicatrix-bearing apex of Suloceras melolineatum 32 (Niko, 1996), a spyroceratid with suborthochoanitic septal Geidoloceras ouaoufilalense sp. nov. 33 necks, shows that a high probability exists that other inter- Plate 6, figure 6; Plate 7, figure 5; Plate 8, figure 5 34 mediate forms have pseudorthoceratid apices. A definite Derivation of name. From the Jebel Ouaoufilal which is close to 35 determination of the higher classification of these ortho- the Filon Douze section. 36 cones is possible only after examination of the shape of the apex. In cases where apical characters are not known I fol- 37 Holotype. MB.C.9627 (Pl. 6, fig. 6; Pl. 7, fig. 5; Pl. 8, fig. 5). 38 low the rule that taxa with typical pseudorthocerid endosip- huncular deposits (parietal deposits) and expanded 39 Type locality and horizon. Filon Douze section, bed KMO-II, 40 siphuncular segments are placed within the Pseudortho- Pragian. 41 cerida, whereas taxa with symmetrical, geisonoceroid endo- 42 siphuncular deposits are placed within the Orthocerida. Material. 1 specimen, MB.C.9629, from bed KMO-III, Pragian, 43 At Filon Douze, apices from Orthocerida exclusively Filon Douze section. 44 were disovered; this is probably a sampling effect caused 45 by the fact that Orthocerida are common and non-Orth- Diagnosis. As for genus, by monotypy. 46 ocerida relatively rare. 47 Description. Holotype with nearly circular cross-section, 21– 48 29 mm in diameter; angle of expansion 10 degrees; ornamented 49 Family PSEUDORTHOCERATIDAE Flower and Caster, 1935 with fine oblique transverse ridges (Pl. 7, fig. 5), sloping slightly 50 towards adoral end on prosiphuncular side; ten ridges occur 8 51 Genus GEIDOLOCERAS gen. nov. within length of 1 mm. In lateral view, prosiphuncular conch mar- gin slightly convex, antisiphuncular margin slightly concave. 52 Type species. Geidoloceras ouaoufilalense sp. nov., from the Pra- Growth axis slightly cyrtoconic with siphuncle at convex side of 53 curvature. Central axis of siphuncle at larger end of holotype 54 gian of the Filon Douze section. 40 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 2 mm off growth axis. Septal distance in holotype 5 mm adapical- Type locality and horizon. Filon Douze section, bed KMO-IV, 2 ly and 8.5 mm adorally. Septal perforation at most apical septum Zlı´chovian, Emsian. 3 in holotype 1.7 mm in diameter, at which point siphuncular seg- 4 ment expands to diameter of 3.8 mm. Siphuncular segments ovate Other material. 2 specimens, MB.C.9656, 9673, from bed F, early 5 with height to width ratio of 1.4–1.5 in holotype. Septal necks cyr- O. costatus conodont Biozone, middle Eifelian, Filon Douze tochoanitic (Pl. 8, fig. 5). Hyposeptal and episeptal deposits occur. 6 section. 7 Diagnosis. Neocycloceras with angle of expansion of c. 8 8 Genus NEOCYCLOCERAS Flower and Caster, 1935 degrees and comparatively narrowly undulating shell; 9 more than four undulations per distance similar to cross- 10 Type species. Neocycloceras obliquum Flower and Caster, 1935, section diameter; undulations slightly oblique, sloping in 11 from the Lewis Run Sandstone Member, Cattaraugus Formation, adoral direction on prosiphuncular side, forming shallow 12 Late Devonian of Lewis Run, Pennsylvania, USA. lobe on prosiphuncular side; sutures more oblique than 13 undulations, projected adaperturally on prosiphuncular 14 Diagnosis (after Sweet 1964b, p. K244). Slender, uncom- side; one undulation between two septa; septal spacing c. 15 pressed to very slightly depressed orthocones with large 0.16 of cross-section diameter; sutures slightly oblique, 16 sinuous, slightly oblique superficial undulations; sutures projecting adaperturally on prosiphuncular side, forming 17 more oblique than undulations, projected adaperturally conspicuous ventral saddle and shallow lateral saddles; 18 on prosiphuncular side; sutural obliquity increasing with siphuncle eccentric with septal perforation 0.25 of conch 19 age; sutures with broad, low dorsal saddle, high, conspic- cross-section; septal necks cyrtochoanitic. 20 uous ventral saddle, and lateral lobes; siphuncle between 21 centre and venter; segments nummuloidal, occupied by Description. Holotype is fragment of phragmocone, 15 mm long, 22 continuous lamellar endosiphuncular deposit, thickest at nearly circular cross-section with diameter 17.8–19.8 mm and 23 widest part of siphuncle and thin in region of neck. angle of expansion 7.6 degrees. Shell surface ornamented with 24 slightly obliquely transverse undulations. Spacing of undulations 25 Remarks. This genus was regarded as questionable by Sweet 4 mm, which is similar to that of septa. Undulations have sharp, 26 (1964b), probably because of the poor knowledge of the narrow ridges and wide, rounded valleys; depth between ridges 27 internal characters of the type. Flower and Caster (1935) and valleys 0.25 mm. Undulations slope slightly in adoral direc- 28 provided no description of the septal neck shape of N. tion on prosiphuncular side. Ridges positioned on adoral surface 29 obliquum. However, it is known that the siphuncle is clearly of septum on antisiphuncular side and on adapical side of suc- ceeding septum on prosiphuncular side (Pl. 5, fig. 6). Septa 30 inflated and it can be deduced from the expanded siphun- slightly oblique, forming shallow lateral lobes and distinctive 31 cular segments that its septal necks are suborthochoanitic 32 saddle on prosiphuncular side. Septal perforation at most adoral or cyrtochoanitic. This is probably the reason why Flower septum 2 mm wide and positioned with centre 8.9 mm from 33 (1939), Shimansky (1962) and Sweet (1964b) placed the conch margin. Septal necks suborthochoanitic, length c. 0.7 mm 34 genus within the Pseudorthoceratidae. Zhuravleva (1978, p. (0.35 of diameter of septal perforation). Traces of connecting 35 150) stated in the generic diagnosis of Neocycloceras that rings in some chambers reveal strongly expanded siphuncular 36 the septal necks are cyrtochoanitic, but provided no evi- segments. 37 dence for this. Herein, I follow the established practice and 38 assign to Neocycloceras species with an ornament similar to Remarks. N? termierorum differs from other species of 39 that of Monomuchites Wilson, 1961, but with obliquely Neocycloceras in having a comparatively narrow undula- 40 lobate sutures, broadly inflated siphuncular segments and tion and a comparatively central siphuncle; it differs from 41 septal necks of pseudortheratid aspect. Neocycloceras differs N. obliquum in its coincidence of chamber height and 42 from Reticycloceras Gordon, 1960 in lacking a longitudinal undulation. In N. obliquum c. 3 camarae occur in the 43 ornamentation. span of one annulation. The septal necks of N? termiero- 44 rum are suborthochoanitic, but clearly longer than in 45 Occurrence. Early Devonian–Late Permian; world-wide. Dawsonoceratidae. The new species is questionably 46 assigned to Neocycloceras because at present the type of 47 this genus is inadequately known. 48 Neocycloceras? termierorum sp. nov. 49 Plate 5, figure 6; Plate 6, figure 4 50 Genus PROBATOCERAS Zhuravleva, 1978 51 Derivation of name. In honour of Genevie`ve and Henri Termier 52 for their lifelong engagement in the palaeontology of Morocco. Type species. Probatoceras crassum Zhuravleva, 1978, from the 53 Frasnian of Sargajevo, South Urals, Russia. 54 Holotype. MB.C.9677 (Pl. 5, fig. 6; Pl. 6, fig. 4). 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 41

1 Emended diagnosis. Short orthocones or slight cyrto- Diagnosis. Straight pseudorthocerids with transversely 2 cones with circular or slightly compressed cross-section; lirate shell; conch cross-section nearly circular; 3–4 septa 3 shell with distinct transverse lirae; septa closely or med- at distance similar to conch diameter; septal necks subor- 4 ium spaced; sutures slightly oblique, sloping towards thochoanitic; siphuncle subcentral; siphuncular segments 5 aperture on prosiphuncular side; siphuncle central or expanded within chambers, elongate-ovate with larger 6 subcentral with expanded segments; septal necks sub- expansion at adoral third of each segment; parietal endo- 7 orthochoanitic; endosiphuncular and cameral deposits siphuncular deposits. 8 not known. 9 Remarks. The presence of suborthochoanitic septal 10 Remarks. In the original diagnosis (Zhuravleva 1978, necks, siphuncular segments of the Dolorthoceras type 11 p.140) the septal necks were described as ‘rather long cyr- (see Flower 1939, fig. 3) and a narrow transverse orna- 12 tochoanitic’ and the siphuncle as ‘central’. However, from mentation are the diagnostic characters of Subdoloceras. 13 the figures of the type it is evident that the septal necks It differs from Dolorthoceras in having a transverse 14 are suborthochoanitic in the strict sense (Kro¨ger and Isa- ornamentation and suborthochoanitic septal necks, and 15 kar 2006). Moreover, the illustration of the type species from Geidoloceras in having suborthochoanitic septal 16 shows that the siphuncle is subcentral. necks. In Dolorthoceras the septal necks of early growth 17 stages are orthochoanitic, becoming cyrtochoanitic in 18 Occurrence. Pragian?–Frasnian; Czech Republic, Morocco and later growth stages. The type species of Subdoloceras is 19 Ural Mountains (Russia). known from early ontogenetic parts of the phragmo- 20 cone, which display suborthochoanitic septal necks. 21 Geidoloceras differs from Subdoloceras in having cyrto- 22 Probatoceras?sp choanitic septal necks and a wider transverse ornamen- 23 Plate 6, figure 12; Plate 8, figure 4 tation. 24 25 Material. 1 specimen, MB.C.9651, from KMO-II, Pragian, Filon Occurrence. Pragian–Daleijan; Morocco. 26 Douze section. 27 28 Description. Fragment of phragmocone 24 mm long, cross-sec- Subdoloceras tafilaltense sp. nov. tion circular, diameter 7.6–10.3 mm (angle of expansion 6.4 29 Plate 5, figure 9; Plate 6, figure 3; Plate 8, figure 3 degrees). Conch surface not preserved. Sutures slightly oblique, 30 slope in adoral direction on prosiphuncular side. Fragment has Derivation of name. From Tafilalt, in which the type locality of 31 eight complete chambers. Distance between two successive septa the species is located. 32 c. 0.2 of conch cross-section; septal perforation subcentral, diam- 33 eter c. 0.1 of conch cross-section. Septal necks suborthochoanit- 34 ic, length 0.3 of septal perforation diameter. Holotype. MB.C.9695 (Pl. 5, fig. 9; Pl. 6, fig. 3). 35 36 Remarks. This specimen cannot be assigned to Probatoc- Type locality and horizon. Filon Douze section, bed KMO-IV, Zlı´chovian, Emsian. 37 eras with certainty because the conch surface, which 38 would yield diagnostic characters, is not preserved. How- Other material. Known only from the holotype. 39 ever, the close septal spacing, the wide angle of expansion, 40 and the shape of the septal necks of this specimen are Diagnosis. Subdoloceras with straight, constantly widening 41 diagnostic characters of Probatoceras. conch with angle of expansion of 12 degrees; cross-section 42 circular; shell surface ornamented with fine, slightly obli- 43 quely transverse lirae; septal spacing c. 0.35 of cross-sec- 44 Genus SUBDOLOCERAS gen. nov. tion diameter; septa directly transverse or slightly oblique; 45 siphuncle subcentral with diameter of septal perforation 46 Type species. Subdoloceras tafilaltense sp. nov., from the Daleijan 0.08 of conch cross-section; siphuncular segments 47 of the Filon Douze section. expanded with point of largest concavity at adoral third 48 of segment; ratio of diameter to length of siphuncular 49 Derivation of name. Latin, sub, beneath, and resemblance to 9 segments c. 0.5; septal necks suborthochoanitic. 50 Dolorthoceras Miller 1931, to indicate the presence of subortho- choanitic septal necks. 51 Description. Holotype is straight fragment of phragmocone, 52 Other species included. Subdoloceras atrouzense sp. nov.; S. enge- 40 mm long, cross-section diameter 10.8–19 mm. Shell surface 53 seri sp. nov. ornamented with fine, slightly obliquely transverse lirae that 54 42 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 slope in adoral direction on prosiphuncular side of conch, four Two additional specimens have poorly preserved shell sur- 2 10occur within distance of 1 mm on adoral part of fragment. Sep- faces. MB.C.9645 19 mm long, diameter 19–22 mm (angle of 3 tal spacing between 6.2 mm at adoral end and 3.9 mm at apical expansion 9 degrees). Distance between septa 4 mm (septal dis- 4 end. Siphuncle subcentral with diameter of septal perforation of tance 0.18 of cross-section diameter). Septal perforation slightly 5 1 mm where cross-section of fragment is 12 mm. Septal necks subcentral. Septal necks suborthochoanitic. MB.C.9682 12 mm suborthochoanitic throughout entire length. Eight septa pre- long, cross-section diameter 4.5–7 mm (angle of expansion 12 6 served in holotype. Siphuncular segments expanded with point degrees). Distance between septa 1.6 mm (septal distance 0.22 of 7 of largest concavity at adoral third of segment (Pl. 8, fig. 3). cross-section diameter). Septal perforation subcentral. Septal 8 Maximum siphuncular diameter at most adapical segment necks cyrtochoanitic. Siphuncular segments strongly expanded 9 1.5 mm. No traces of endosiphuncular or cameral deposits within chambers, ovate and adnate on adoral surfaces of septa; 10 occur. length to height ratio 1.4. 11 12 Remarks. This species differs from S. engeseri sp. nov. in Remarks. This species of Subdoloceras is characterized by 13 having a lower expansion rate and a less eccentric siphun- its high expansion rate. 14 cle. 15 16 Subdoloceras engeseri sp. nov. 17 Subdoloceras atrouzense sp. nov. Plate 6, figure 5; Plate 7, figure 2; Plate 8, figure 7 18 Plate 6, figure 1; Plate 7, figure 1; Plate 8, figure 1 19 Derivation of name. In honour of Theo Engeser, Berlin, for his 20 Derivation of name. From the El Atrouz mine to the east of the compilation of a comprehensive taxonomic database of non- 21 Filon Douze section. ammonoid cephalopods. 22 23 Holotype. MB.C.9595 (Pl. 6, fig. 1; Pl. 7, fig. 1; Pl. 8, fig. 1). Holotype. MB.C.9654 (Pl. 8, fig. 7). 24 25 Type locality and horizon. Filon Douze section, bed KMO-II, Type locality and horizon. Filon Douze section; bed KMO-I, 26 Pragian. Pragian. 27 Other material. 15 specimens, MB.C.9657–72, from bed KMO- 28 Other material. 3 specimens, MB.C.9681–82, 9645, from beds KMO-II and KMO-III, Pragian, Filon Douze section. II, Pragian, Filon Douze section. 29 30 Diagnosis. Subdoloceras with slightly cyrtoconic conch; Diagnosis. Subdoloceras with angle of expansion of 7–9 31 angle of expansion 15 degrees; cross-section circular or degrees; cross-section circular or slightly depressed; orna- 32 slightly compressed; ornamented with fine, obliquely mented with fine, obliquely transverse rounded ridges 33 transverse rounded ridges; septal spacing c. 0.2 of cross- with narrow interspaces; ridges slope in adoral direction 34 section diameter; septa slightly oblique, sloping in adoral on prosiphuncular side; septal spacing 0.3–0.4 of cross- 35 direction on prosiphuncular side; siphuncle subcentral section diameter; septa slightly oblique, sloping in adoral 36 with diameter of septal perforation 0.1 of conch cross-sec- direction on prosiphuncular side; obliquity of ornamenta- 37 tion; septal necks suborthochoanitic. tion stronger than that of septa; sutures straight; siphun- 38 cle subcentral with septal perforation 0.1 of conch cross- 39 Description. Holotype is fragment of phragmocone 23 mm long, section; siphuncular segments expanded with maximum 40 cross-section diameter 8–14.5 mm, ornamented with slightly diameter c. 0.14 of conch cross-section; septal necks sub- 41 obliquely transverse ridges that slope towards adoral end on orthochoanitic; parietal endosiphuncular deposits strongly 42 11 prosiphuncular side (Pl. 7, fig. 1). Ten ridges occur within elongated in direction of apex, slightly touching connect- 43 length of 1 mm. In lateral view conch margins slightly concave. ing ring at septal necks; hyposeptal and episeptal deposits. 44 Growth axis very slightly curved with subcentral siphuncle on convex side of growth axis. Septal spacing 2.9 mm at adoral end 45 Description. Holotype with nearly straight growth axis; nearly and 1.5 mm at apical end. Septal perforation of 1.5 mm at most 46 circular cross-section 15–19 mm in diameter; angle of expansion adoral septum. Septal necks suborthochoanitic (Pl. 7, fig. 1). 47 of conch 9 degrees, ornamented with fine, transverse oblique li- Holotype shows no traces of connecting ring, endosiphuncular 48 rae, sloping slightly towards adoral end on pre-siphuncular side or cameral deposits. 49 13(Pl. 7, fig. 2). Twenty lirae occur within length of 1 mm. Angle MB.C.9681 is fragment of phragmocone 26 mm long; cross- 50 of expansion 7 degrees in MB.C.9658, with maximum cross-sec- section nearly circular, diameter c. 12–18 mm (angle of expan- tion diameter of 15 mm, 8 degrees in MB.C.9657, with maxi- 51 sion 15 degrees). Conch margin in median section slightly mum cross-section diameter of 16 mm. In holotype, septal 52 convex. Surface transversely ornamented with ten ridges at distance between 5 mm adapically and 6 mm adorally, central 53 12length of 1 mm. 54 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 43

1 axis of siphuncle apically at distance of 1.4 mm from growth Type locality and horizon. Filon Douze section, Erbenoceras 2 axis, diameter of septal perforation at most adoral septum Limestone, Zlı´chovian, Emsian. 3 1.6 mm. Siphuncular segments expanded with length to height 4 ratio of 1.4 in MB.C.9659, 1.5 in MB.C.9660. Septal necks subor- Other material. 1 specimen, MB.C.8684, from the type locality 5 thochoanitic (Pl. 8, fig. 7). In smaller fragments, siphuncular and horizon; 3 specimens, MB.C.9571.1–3, from bed F, P. parti- tube appears less expanded with ratio of height to length of sip- 6 tus conodont Biozone, Eifelian, the type locality. huncular segments 2.0. Parietal endosiphuncular deposits occur 7 in MB.C.9658 at a cross-section diameter <11 mm. Diagnosis. Slender, straight conch with nearly circular 8 cross-section; angle of expansion very low; sutures 9 Remarks. This species differs from S. tafilaltense sp. nov. straight transverse; septal distance 0.3 of conch cross-sec- 10 in having a relatively low expansion rate and a more tion; siphuncle nearly central; siphuncular segments sub- 11 eccentric siphuncle. globular with width to height ratio of c. 1.0; siphuncular 12 diameter c. 0.12 of cross-section; septal necks subortho- 13 choanitic, forming rounded brim; length of septal necks c. 14 Genus SUBORMOCERAS gen. nov. 0.15 of septal distance, 0.3 of diameter of septal perfora- 15 tion; episeptal deposits. 16 Type species. Subormoceras erfoudense sp. nov., from the Zlı´cho- 17 vian (Emsian) of the Filon Douze section. Description. Holotype 50 mm long, with slightly compressed 18 cross-section 36–38 mm in diameter (angle of expansion c. 1 19 Derivation of name. Latin, sub, under, referring to the subortho- degree). Surface poorly preserved but apparently smooth. Frag- 20 choanitic septal necks of this genus, which otherwise is similar ment displays seven complete chambers. Distance between two 21 to Ormoceras. most adoral septa 13 mm, and between most adapical 8 mm. 22 Septal curvature with depth of 12 mm at most adoral septum. 23 Other species included. Ormoceras dobrovljanense Kiselev, in Bala- Sutures straight, transverse. Septal perforation 5 mm in cross- 24 shov and Kiselev 1968; O. rashkovense Kiselev, in Balashov and section. Septal necks suborthochoanitic, form c. 1.5-mm-long, 25 Kiselev 1968; O. skalaense Kiselev, in Balashov and Kiselev 1968 rounded brims. Siphuncle subcentral. Centre of septal perfora- 26 (all species combined with Ormoceras below: see ‘List of new tion 21 mm from conch margin. Siphuncular segments combinations’); S. rissaniense sp. nov. 27 expanded within chambers, height and width about equal. Endo- 28 siphuncular and cameral deposits unknown. Diagnosis. Straight conch with nearly circular cross-sec- MB.C.8684 33 mm long, maximum conch cross-section 29 tion; angle of expansion <10 degrees; sutures straight, 35 mm, with three complete chambers preserved 10, 8.9 and 30 transverse; septal distance small, <0.3 of conch cross-sec- 8.0 mm in length from adoral to adapical end. Septal per- 31 tion; siphuncle central–eccentric; siphuncular segments foration nearly central, 4 mm in diameter. Episeptal deposits 32 expanded within chambers, elliptical or subcircular in present. 33 median section, without area of adnation; septal perfora- 34 tion c. 0.1–0.15 of conch cross-section; septal necks sub- Remarks. This species is very similar to Ormoceras dob- 35 orthochoanitic; endosiphuncular deposits not known; rovljanense Kiselev, in Balashov and Kiselev 1968; from 36 episeptal deposits. which it differs only in having a more slender siphuncle 37 that is positioned closer to the growth axis. 38 Remarks. This genus differs from Ormoceras in having 39 suborthochoanitic septal necks and there are either no en- 40 dosiphuncular deposits or they are restricted to the very Subormoceras rissaniense sp. nov. 41 adapical parts of the phragmocone of mature specimens. Plate 4, figure 10; Plate 8, figure 9 42 Subdoloceras differs in having a narrower siphuncle and a 43 wider septal spacing. Derivation of name. From Rissani, in eastern Tafilalt. 44 45 Holotype. MB.C.9678 (Pl. 8, fig. 9). Occurrence. Ludfordian to Eifelian; Morocco and Ukraine. 46 47 Type locality and horizon. Filon Douze section, bed PI, early O. 48 costatus conodont Biozone, middle Eifelian. Subormoceras erfoudense sp. nov. 49 Plate 8, figure 6 50 Other material. 1 specimen, MB.C.9622, from bed F, P. partitus conodont Biozone, Eifelian, Filon Douze section. 51 Derivation of name. From Erfoud in south-east Tafilalt. 52 Diagnosis. Straight conch with nearly circular cross-sec- 53 Holotype. MB.C.9683 (Pl. 8, fig. 6). 54 tion; angle of expansion below 9 degrees; sutures straight, 44 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 transverse; septal distance 0.15 of conch cross-section; sip- Remarks. This species is very distinctive because of the 2 huncle subcentral; siphuncular segments expanded within convex shape of the conch margins in median section 3 chambers; siphuncular diameter c. 0.1 of cross-section; and the angular shape of the suborthochoanitic septal 4 septal necks suborthochoanitic and form angular brim; necks. 5 length of septal neck c. 0.3 of septal distance, 0.5 of diam- 6 eter of septal perforation; endosiphuncular and cameral 7 deposits unknown. Subormoceras sp. 8 Plate 4, figures 6–7; Plate 8, figure 10 9 Description. Holotype 50 mm long, slightly compressed cross- 10 section, diameter of 42–43 mm (angle of expansion 9 degrees). Material. One specimen, MB.C.9674 from bed OSP-I, Prˇı´dolı´, 11 Conch straight, margins slightly convex in median section. Filon Douze section. 12 Surface poorly preserved in holotype but second specimen has 13 a smooth surface with faint, irregularly spaced, growth lines. Description. Conch fragment 40 mm long; cross-section 31– Holotype displays nine complete chambers. Distance 14 35 mm in diameter (angle of expansion 6 degrees); margins between two most adoral septa 5.4 mm, between most adapi- 15 slightly convex in median section; cross-section slightly com- cal chambers 5.5 mm. Septal curvature with depth of 3.8 mm pressed, ratio of conch width to height 0.93, subtriangular with 16 at most adoral septum. Sutures straight, transverse. Septal flattened antisiphuncular side and rounded lateral side. Conch 17 perforation of most adoral septum 3 mm in cross-section. surface poorly preserved but smooth or only slightly orna- 18 Septal necks suborthochoanitic and form c. 1.5-mm-long, mented, without undulations. Sutures form shallow lateral sad- 19 angular brims. Siphuncle subcentral. Centre of septal perfora- dles and wide lobe on prosiphuncular side. Septal distance 20 tion 15.6 mm from conch margin at most adoral septum. between 5.3 and 4.1 mm (0.16–0.13 of cross-section diameter). 21 Siphuncular segments expanded within chambers but their Septa imploded and fragmentary, providing no information on 22 shape is not known. Endosiphuncular and cameral deposits exact position of siphuncle, which is not marginal. Diameter of 23 unknown. septal perforation 4 mm (0.14 of conch cross-section). Septal 24 Second specimen ornamented with very fine, directly trans- necks suborthochoanitic to orthochoanitic, 1.4 mm long (Pl. 8, verse, growth lines 63 mm long, conch cross-section 33–40 mm 25 fig. 10). in diameter. Conch margins slightly convex in median section. 26 Only most adoral septum completely preserved, showing septal 27 Remarks. The very close septal spacing and the subortho- perforation 4.4 mm in cross-section and suborthochoanitic sep- choanitic septal necks are diagnostic characters of Subor- 28 tal necks, which form angular brims. 29 30 31 32 EXPLANATION OF PLATE 5 33 Median sections of Oncocerida, Actinoceratida and Pseudorthocerida from the Filon Douze section. 34 Fig. 1. Mutoblakeoceras inconstans gen. et sp. nov., MB.C.9584; bed PI, early O. costatus conodont Biozone, middle Eifelian; detail of 35 siphuncular structure, conch margin on the right; note the concave appearance of siphuncular segments, orthochoanitic septal 36 necks and endosiphuncular lamellae. 37 Fig. 2. Indet. Nothoceratidae sp. A., MB.C.9635; bed PI, early O. costatus conodont Biozone, middle Eifelian; detail of siphuncular 38 structure, conch margin towards the left; note the concave appearance of siphuncular segments, orthochoanitic septal necks and 39 endosiphuncular lamellae. 40 Fig. 3. Ormoceras sp., MB.C.9639; bed KMO-I, Pragian; note the cyrtochoanitic septal necks and the irregularly shaped, massive 41 ventral endosiphuncular annuli. 42 Figs 4–5. Metarmenoceras fatimae sp. nov., MB.C.9674. holotype; Erbenoceras Limestone, Zlı´chovian, Emsian. 4, detail of siphuncular 43 structure; note the recumbent septal necks, the large area of adnation of the connecting ring, and the massive endosiphuncular 44 deposits. 5, entire specimen. 45 Fig. 6. Neocycloceras? termieri sp. nov., MB.C.9677, holotype; bed KMO-IV, Daleijan, Emsian; detail of septal perforation showing 46 cyrtochoanitic septal necks. 47 Figs 7–8. Deiroceras hollardi sp. nov., MB.C.9630; Deiroceras Limestone, Zlı´chovian, Emsian. 7, entire specimen; note the large, 48 elliptical siphuncular segments. 8, detail of siphuncular structure showing suborthochoanitic septal necks and massive 49 endosiphuncular annuli. 50 Fig. 9. Subdoloceras tafilaltense gen. et sp. nov., MB.C.9695, holotype; bed KMO-IV, Daleijan, Emsian; detail of septal perforation 51 showing suborthochoanitic septal necks. 52 Fig. 10. Diagoceras sp., MB.C.9579, bed PI, early O. costatus conodont Biozone, middle Eifelian; section shows oblique, narrowly 53 spaced septa and suborthochoanitic septal necks. 54 Scale bars represent 1 mm; figures without a scale bar are ·1. PLATE 5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 1 2 3 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 5 4 6 37 38 39 40 41 42 43 44 45 46 47 48 49 7 50 51 52 53 10 mm 54 8 9 10 KRO¨ GER, Actinoceratida, Oncocerida, Pseudorthocerida 46 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 moceras. However, the exact position of the septal perfo- Holotype. MB.C.9676 (Pl. 8, figs 8, 11). 2 ration and the shape of the siphuncular segments are not 3 known, making a specific determination of the fragment Type locality and horizon. Filon Douze section, bed KMO-III, 4 impossible. Pragian. 5 6 Other material. 1 specimen, MB.C.9649, from the type locality and horizon. 7 Family SPYROCERATIDAE Shimizu and Obata, 1935a 8 Diagnosis. Cyrtoconic Spyroceras with angle of expansion 9 Remarks. I follow the diagnosis of Sweet (1964b,p. of 12–15 degrees; cross-section slightly compressed; conch 10 K246) in assigning to the Spyroceratidae orthocones that with straight undulations; surface ornamented with c. 11 have siphuncular segments and endosiphuncular deposits 150–200 distinctive, raised, irregularly spaced, longitudi- 12 with the aspect of Dolorthoceras. The septal necks of nal lirae around circumference and numerous faint, 13 Spyroceras are cyrtochoanitic; those of Dolorthoceras are directly transverse lirae; approximately two transverse li- 14 cyrtochoanitic in adult growth stages and suborthocho- rae at distance similar to distance between two longitudi- 15 anitic in juvenile stages (see Flower 1939, fig. 3). The nal lirae; septa directly transverse at distance of c. 0.25 of 16 septal necks and siphuncular segments of Cancellspyroc- cross-section diameter; septal perforation c. 0.1 of conch 17 eras gen. nov. and Suloceras Manda, 2001, resemble cross-section diameter; septal necks cyrtochoanitic; sip- 18 those of juvenile Dolorthoceras. I place these two genera huncle subcentral on convex side of conch curvature. 19 within the Spyroceratidae because, in addition to their 20 Dolorthoceras-like septal neck shape, they have Spyroc- Description. Holotype is fragment of phragmocone 32 mm long; 21 eras-like ornamentation. compressed cross-section with width to height ratio of 0.92, diam- 22 eter 6–13 mm (angle of expansion 12 degrees). Conch cyrtoconic 23 with siphuncle slightly shifted from centre towards convex side of 24 Genus SPYROCERAS Hyatt, 1884 conch curvature. MB.C.9649 39 mm long, cross-section diameter 25 6.5 –17 mm (angle of expansion 15 degrees). Surface of holotype 26 Type species. Orthoceras crotalum Hall, 1879, from the Skanea- poorly preserved with distance between longitudinal lirae at adoral 27 teles Shale, Hamilton stage, Devonian, of Pratt’s Fall, Onondaga end averaging 0.3 mm, transverse lirae at distances of 0.1 mm; dis- 28 County, New York, USA. tance between longitudinal lirae variable. MB.C.9649 has, at adoral 29 end (cross-section diameter 17 mm), irregularly spaced longitudi- 30 Diagnosis (after Sweet 1964b, p. K246). Undulating or- nal lirae at distances of c. 0.3 mm (Pl. 6, fig. 9; Pl. 7, fig. 4) and 31 thocones with straight, transverse sutures, transverse or directly transverse shallow undulations at distances of c. 4 mm. Holotype has 12 septa with chamber height of 3 mm at adoral 32 slightly oblique undulations and faintly cyrtoconic apices; end, 1.5 mm at adapical end. Shallow septal concavity with depth 33 surface ornamented with longitudinal lirae conspicuous from earliest stage and with transverse elements; siphun- of curvature 2.9 mm at most adoral chamber. Septal perforation 34 at most adoral septum of holotype 1 mm wide. Septal necks cyrto- cle central or slightly ventrally shifted from centre; 35 choanitic (Pl. 8, figs 8, 11). Siphuncular segments slightly 36 siphuncular segments and endosiphuncular deposits of expanded within chambers; siphuncle subcentral. Siphuncular seg- 37 Dolorthoceras type (Flower 1938); septal necks cyrtocho- ments with height to width ratio of c. 1.7. 38 anitic; cameral deposits developing later than in other 39 Pseudorthoceratidae, hence confined to more apical Remarks. This species differs from S. patronus in having a 40 regions of conch. higher expansion rate, a cyrtoconic conch and more clo- 41 sely spaced longitudinal ornamentation, and from S. late- 42 Occurrence. The time range and geographical occurrence of the patronus sp. nov. in having a lesser angle of expansion 43 genus is difficult to assess because it serves as a ‘wastebasket’ and less regular longitudinal ornamentation. taxon for orthocones with similar ornamentation but different 44 internal characters. It seems to be restricted to the Devonian and 45 has a world-wide distribution. 46 Spyroceras fukuijense? Niko, 1996 47 Plate 6, figure 11; Plate 7, figure 9; Plate 9, figure 4 48 Spyroceras cyrtopatronus sp. nov. *1996 Spyroceras fukuijense Niko, p. 350, figs 3, 3–11, 49 Plate 6, figure 9; Plate 7, figure 4; Plate 8, figures 8, 11 50 figs 4, 1–5. 51 Derivation of name. Greek, kyrtos, curved, with reference to the Material. 2 specimens, MB.C.9776–77, from KMO-III, Pragian, 52 bent growth axis of this species, which is otherwise similar to S. Filon Douze section. 53 patronus (Barrande, 1866). 54 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 47

1 Diagnosis (after Niko 1996, p. 350). Slightly cyrtoconic distance of c. 0.2 of cross-section diameter; septal perfora- 2 Spyroceras with low angle of expansion; cross-section cir- tion width c. 0.15 of cross-section diameter; septal necks 3 cular or slightly depressed; conch with straight undula- cyrtochoanitic, siphuncle subcentral on convex side of 4 tions; undulations less distinctive in later growth stages; conch curvature. 5 ornamented with 25–33 distinctive, raised, longitudinal li- 6 rae around circumference and numerous faint, directly Description. Holotype 22 mm long, cross-section diameter 8– 7 transverse lirae; additionally, reticulate ornamentation 13 mm (angle of expansion 16 degrees). Cross-section nearly cir- 8 occurs on body chamber; siphuncle slightly subcentral on cular. Conch slightly cyrtoconic with siphuncle slightly shifted 9 concave side of conch curvature. from centre towards convex side of conch curvature, slightly 10 obliquely undulating (Pl. 6, fig. 7). Distance between undula- tions 3.5 mm. Longitudinal lirae 0.3 mm apart, transverse lirae 11 Description. Larger specimen (MB.C.9777) 17 mm long, cross- 0.1 mm apart. Vertical lirae as distinctive as transverse lirae. In section diameter 16–18 mm (angle of expansion 7 degrees). Sur- 12 longitudinal section on prosiphuncular side slightly concave, on face ornamented with 26 prominent longitudinal lirae (Pl. 6, fig. 13 antisiphuncular side slightly convex. Distance between chambers 11). Undulations directly transverse with distances of c. 5 mm. 14 2.5–3.5 mm. Septal perforation has diameter of 0.6 mm with Distance between transverse striae 3–4 mm. Septal distance 15 cyrtochoanitic septal necks and expanded siphuncular segments. 4.5 mm. Septal perforation slightly shifted from growth axis 16 Siphuncular segments with height to width ratio of c. 1.7. Epi- towards concave side of conch curvature with diameter of septal and mural deposits present. 17 2.2 mm at cross-section diameter of 17 mm (MB.C.9777). Septal MB.C.9779 35 mm long, maximum diameter 21 mm. Conch 18 necks suborthochoanitic (Pl. 9, fig. 4). 19 fragmented; angle of expansion >13 degrees. Conch surface poorly preserved but about three transverse lirae at distance sim- 20 Remarks. The specimens described above display the 21 ilar to distance between longitudinal lirae. Septal distance at diagnostic characters of the phragmocone of S. fukuijense. adoral end 4 mm. Septal perforation 1.5 mm in diameter at api- 22 However, fragments of the adult body chamber of this cal end. Septal necks cyrtochoanitic (Pl. 9, fig. 1). 23 species are not known from Filon Douze. Because the 24 body chamber of S. fukuijense shows a conspicuous retic- Remarks. This species differs from S. patronus in having a 25 ulate ornamentation that has diagnostic value, the Filon higher expansion rate and more‘widely spaced transverse 26 Douze fragments cannot be assigned to the species with ornamentation. 27 certainty. 28 29 Occurrence. Lochkovian to Pragian; Japan and Morocco. Spyroceras patronus (Barrande, 1866) 30 Plate 7, figure 6; Plate 9, figure 3 31 32 Spyroceras latepatronus sp. nov. *1866–70 Orthoceras patronus Barrande, pl. 228, figs 5–6; 33 Plate 6, figure 7; Plate 7, figure 3; Plate 9, figures 1–2 pl. 262, figs 12–13; pl. 275, figs 20–28; pl. 445, 34 figs 9–11. 35 Derivation of name. Latin, latus, wide, referring to the wide 1885 Orthoceras patronus Barrande; Tschernyschev, p. 10, 36 angle of expansion of this species compared with S. patronus. pl. 1, figs 10–11. 37 1978 Spyroceras patronus (Barrande); Zhuravleva, pp. 89, 38 Holotype. MB.C.9653 (Pl. 6, fig. 7; Pl. 7, fig. 3). 94. 39 1984 Orthoceras patronus Barrande; Dzik, p. 125, 40 Type locality and horizon. Filon Douze section, bed KMO-I, text-fig. 49.17. 41 Pragian. 42 Material. 1 specimen, MB.C.9652, from bed KMO-I and 1 speci- men, MB.C.9778, from KMO-II, Pragian, Filon Douze section. 43 Other material. 2 specimens, MB.C.9779, 9694, from the type 44 locality and horizon. Diagnosis. Slightly cyrtoconic Spyroceras with variable 45 Diagnosis. Slightly cyrtoconic Spyroceras with variable angle of expansion of 6–12 degrees; cross-section circular 46 angle of expansion of more than 15 degrees; cross-section or slightly depressed; adult body chamber with cross-sec- 47 circular or slightly depressed; conch with oblique undula- tion diameter of c. 35 mm, adorally slightly contracted; 48 tions, sloping in adoral direction on convex side of conch conch with oblique undulations, sloping in adoral direc- 49 curvature; surface ornamented with c. 60 distinctive, tion on convex side of conch curvature; undulations less 50 raised, longitudinal lirae around circumference and distinctive in later growth stages and disappear at adult 51 numerous faint, directly transverse lirae; approximately body chamber; surface ornamented with c. 60 distinctive, 52 three transverse lirae at distance similar to distance raised, longitudinal lirae around circumference and 53 between two longitudinal lirae; septa directly transverse at numerous faint, directly transverse lirae; c. 5–10 lirae at 54 48 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 distance similar to distance between two longitudinal li- Spyroceras? sp. A. 2 rae; septa directly transverse at distance of c. 0.2 of conch Plate 7, figure 7 3 cross-section; septal perforation width c. 0.15 of conch 4 cross-section; septal necks cyrtochoanitic; siphuncle sub- Material. 1 specimen, MB.C.9698, from bed KMO-III, Pragian, 5 central on convex side of conch curvature; siphuncular Filon Douze section. 6 segments expanded within chambers. 7 Description. Fragment slightly cyrtoconic, 25 mm long, cross- 8 Description. Specimen MB.C.9778 32 mm long, cross-section section slightly compressed 20–24 mm in diameter (angle of expansion 9 degrees). Conch shallowly undulating with distance 9 diameter 20–24 mm (angle of expansion 10 degrees). MB.C.9652 between undulations 5 mm, longitudinal raised lirae 1 mm apart 10 36 mm long, cross-section diameter 17–22 mm (angle of expan- sion 8 degrees). Distance between longitudinal striae 1 mm, (75 lirae occur across circumference), directly transverse, regu- 11 larly spaced lirae 0.3 mm apart. Undulations describe shallow 12 between transverse striae 0.2 mm, in both specimens. Septal per- foration subcentral on convex side of conch curvature with lateral lobes. Distance between septa 3.5 mm. Septal concavity 13 diameter of 2.5 mm at cross-section diameter of 20 mm shallow. Septal perforation subcentral with diameter 1.1 mm at 14 (MB.C.9697). Septal necks short, suborthochoanitic to cyrtocho- adapical end of fragment (0.16 of conch-cross-section). 15 anitic (Pl. 9, fig. 3). 16 Remarks. This fragment displays the external characters 17 Remarks. The specific diagnosis refers to the excellent fig- of Spyroceras but the internal characters are unknown. 18 ures of ‘Orthoceras’ patronus of Barrande, 1868), which The species differs from S. patronus in having 75, as 19 include details of the siphuncle, septal necks and adult opposed to c. 60, longitudinal lirae around the circumfer- 20 characters. Spyroceras patronus differs from Suloceras pul- ence. 21 chrum (Barrande, 1868) in having a slightly cyrtoconic 22 conch and a higher expansion rate. The ornamentation of 23 S. pulchrum also differs in consisting of alternating prom- Spyroceras? sp. B. 24 inent and subordinate longitudinal lirae. The fragments Plate 7, figure 8 25 from Filon Douze here referred to S. patronus differ from 26 Barrande’s specimens in having a larger angle of expan- Material. 1 specimen, MB.C.9699, from bed KMO-III, Pragian, 27 sion. These variations are regarded as intraspecific. How- Filon Douze section. 28 ever, two specimens from the Prˇı´dolı´ of Filon Douze that Description. Fragment slightly cyrtoconic, 30 mm long, slightly 29 are otherwise similar to S. patronus conspicuously deviate compressed cross-section with diameter of 13–16 mm (angle of 30 from the moderate expansion rate of the type figured in 31 expansion 6 degrees). Conch strongly undulating with distance Barrande (1868, pl. 275, figs 20, 24–26); these are between undulations 4 mm; irregularly spaced, longitudinal 32 assigned to S. latepatronus sp. nov. Spyroceras patronus raised lirae 0.4 mm apart (c. 100 lirae occur around circumfer- 33 differs from S. fukuijense Niko, 1996 in having a higher ence); directly transverse, regularly spaced lirae 0.1 mm apart. 34 number and less prominent longitudinal striae and a Septal concavity shallow. 35 wider angle of expansion. 36 Remarks. The fragment displays the external characters of 37 Occurrence. Pragian; Czech Republic, Kazakhstan and Morocco. Spyroceras but the internal characters of the fragment are 38 39 40 41 EXPLANATION OF PLATE 6 42 Fig. 1. Subdoloceras atrouzense gen. et sp. nov., MB.C.9595, holotype; bed KMO-II, Pragian; lateral view with epizoan. 43 Fig. 2. Sphooceras truncatum (Barrande, 1860), MB.C.9801; bed OP-M, Ludfordian, Ludlow; lateral view. 44 Fig. 3. Subdoloceras tafilaltense gen. et sp. nov., MB.C.9695, holotype; bed KMO-IV, Daleijan, Emsian; lateral view. 45 Fig. 4. Neocycloceras? termieri sp. nov., MB.C.9677, holotype; bed KMO-IV, Daleijan, Emsian; lateral view. 46 Fig. 5. Subdoloceras engeseri gen. et sp. nov., MB.C.9657; bed KMO-I, Pragian; lateral view. 47 Fig. 6. Geidoloceras ouaoufilalense gen. et sp. nov., MB.C.9627, holotype; bed KMO-III, Pragian; lateral view. 48 Fig. 7. Spyroceras latepatronus sp. nov., MB.C.9653, holotype; bed KMO-I, Pragian; lateral view. 49 Fig. 8. Spyroceras sp. B., MB.C.9699; bed KMO-III, Pragian; lateral view. 50 Fig. 9. Spyroceras cyrtopatronus sp. nov., MB.C.9649; bed KMO-III, Pragian; lateral view. 51 Fig. 10. Reticuloceras loricatum (Barrande, 1868), MB.C.9646; bed KMO-II, Pragian; lateral view. 52 Fig. 11. Spyroceras fukuijense? Niko, 1996, MB.C.9777; bed KMO-III, Pragian; lateral view. 53 Fig. 12. Probatoceras?sp., MB.C.9651; bed KMO-II, Pragian; lateral view. 54 All specimens from the Filon Douze section and ·2. PLATE 6 1 2 3 4 5 6 7 8 9 10 2 11 1 12 13 14 15 16 17 18 19 20 21 3 22 4 23 24 5 25 26 27 28 29 6 30 31 32 33 34 7 35 36 37 38 39 8 40 41 42 9 43 44 45 46 47 48 49 50 51 52 53 10 11 12 54 KRO¨ GER, nautiloids 50 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 unknown. The species differs from S. patronus in having septa directly transverse c. 0.3 of cross-section diameter; 2 100, as opposed to c. 60, longitudinal lirae around the septal perforation width c. 0.1 of cross-section diameter; 3 circumference. septal necks short, suborthochoanitic; siphuncle subcen- 4 tral on convex side of conch curvature. 5 6 Genus CANCELLSPYROCERAS gen. nov. Description. Larger specimen (MB.C.9646) 24 mm long, cross- 7 section diameter 37–41 mm (angle of expansion 10 degrees). 8 Type species. Orthoceras loricatum Barrande, 1868, from the Smaller specimen (MB.C.9686) 21 mm long, cross-section diam- 9 Lower Devonian of Bohemia, Czech Republic. eter 23–26 (angle of expansion 8 degrees). Cross-section of spec- 10 imens circular or slightly compressed. Ornamentation consists of equally raised transverse and longitudinal lirae (Pl. 7, fig. 10). 11 Derivation of name. Latin, cancellus, lattice, referring to the net- like ornamentation of this genus. Distance between longitudinal lirae 0.5 mm, between transverse 12 striae 0.3–0.4 mm in MB.C.9646. Sutures straight and transverse. 13 Other species included. None. Distance between septa 0.3–0.4 of cross-section diameter 14 (12 mm at cross-section diameter of 41–31 mm; 8 mm at cross- 15 section diameter of 26 mm). Septal perforation 3 mm at cross- Diagnosis. Very slightly cyrtoconic pseudorthocerids with 16 section diameter of 26 mm. Septal necks suborthochoanitic (Pl. reticulate ornamentation consisting of conspicuous, raised 17 8, fig. 2). longitudinal and transverse lirae; angle of expansion c. 11 18 degrees; Conch cross-section nearly circular. Approxi- 19 Remarks. The type of ‘Orthoceras’ loricatum figured in Bar- mately four septa at distance similar to conch diameter; 20 rande (1868, 1870) provides no information on the posi- septal necks short suborthochoanitic; siphuncle sub- 21 tion and shape of the siphuncle or of the characters of the central. 22 septal necks. Therefore, to synonymize the specimens from 23 Filon Douze with it is a little doubtful, but the fragments Remarks. Cancellspyroceras differs from Spyroceras in hav- 24 described are similar to ‘O.’ loricatum in general conch ing suborthochoanitic septal necks and a shell that is not 25 shape, ornamentation, and septal spacing. Zhuravleva undulating. The ornamentation of Cancellspyroceras 26 (1978, p. 140) assigned ‘O.’ loricatum to Probatoceras and resembles that of Protokionoceras Grabau and Shimer, 27 Manda (2001, fig. 6.) placed it in Protokionoceras, but nei- 1910. The internal characters of the mid Silurian type of 28 ther author gave reasons for their decisions. Protokionoceras are poorly known; however, Sweet 29 Cancellspyroceras loricatum differs from Spyroceras in (1964b) wrote ‘Siphuncle and cameral deposits in at least 30 having suborthochoanitic septal necks and in lacking some species similar to those of Geisonoceras’. The Eif- 31 undulation. elian Nebroceras Zhuravleva, 1978, has a similar ornamen- 32 tation but differs in having septal necks that are 33 Occurrence. Pragian; Czech Republic and Morocco. asymmetric along the dorsoventral axis. 34 35 Occurrence. Early Devonian; Czech Republic and Morocco. 36 Genus DIAGOCERAS Flower, 1936 37 38 Type species. Orthoceras aptum Hall, 1876, from the Cherry Val- Cancellspyroceras loricatum (Barrande, 1868) 39 ley Limestone, Givetian of New York, USA. Plate 6, figure 10; Plate 7, figure 14; Plate 8, figure 2 40 41 Diagnosis (after Flower 1936, p. 293; Zhuravleva 1978, p. *1868–70 Orthoceras loricatum Barrande, pl. 275, figs 10–13; 127). Slender, smooth or transversely ornamented ortho- 42 pl. 424, figs 5–8. 43 cones with circular or depressed cross-section; sutures 1978 Protobatoceras loricatum (Barrande); Zhuravleva, oblique, sloping adapically on antisiphuncular side of 44 p. 140. conch; siphuncle subcentral; septal necks suborthochoan- 45 2001 Protokionoceras loricatum (Barrande); Manda, p. 6. 46 itic; siphuncular segments slightly expanded within cham- 47 Material. 2 specimens, MB.C.9646, 9686, from KMO-II, Pragian, bers; mature living chamber slightly constricted; cameral 48 Filon Douze section. deposits mural. 49 50 Diagnosis. Slightly cyrtoconic with variable angle of Remarks. The oblique septa and subcentral siphuncle are 51 expansion of c. 11 degrees; cross-section circular; surface characters of Plagiostomoceras, which differs from Diagoc- 52 ornamented with numerous longitudinal and directly eras in having orthochoanitic septal necks. Diagoceras was 53 transverse, distinctive raised lirae; longitudinal and trans- assigned to the Pseudorthoceratidae by Flower (1939), 54 verse lirae form conspicuous net-like rectangular pattern; but its close similarity to Adiagoceras gen. nov. suggests a 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 51

1 relationship with the Arionoceratidae (see below). A defi- Occurrence. Lochkovian–Pragian; Czech Republic, Japan and 2 nite decision with regard to the higher classification of Morocco. 3 this genus will not be possible until its apical characters 4 are better known. 5 Suloceras longipulchrum sp. nov. 6 Occurrence. Eifelian to Frasnian; Morocco, North America and Plate 7, figure 10; Plate 9, figure 5; Plate 10, figure 1 7 Russia. 8 Derivation of name. Latin, longus, long, referring to the wide 9 septal spacing of this species compared with other Suloceras, 10 Diagoceras sp. especially the similar S. pulchrum. 11 Plate 5, figure 10 Holotype. MB.C.9783 (Pl. 7, fig. 10; Pl. 9, fig. 5; Pl. 10, fig. 1). 12 13 Material. 1 specimen, MB.C.9579, from bed PI, early O. costatus conodont Biozone, middle Eifelian, Filon Douze section. Type locality and horizon. Filon Douze section, bed KMO-III, 14 Pragian. 15 16 Description. Fragment of phragmocone 62 mm long, conch height 13–28 mm (angle of expansion 14 degrees). Cross-section Material. 2 specimens, MB.C.9784–85, from the type locality 17 slightly depressed. Distance between septa 2.3 mm at apical end and horizon. 18 of fragment. Septal concavity 2.8 mm at most adapical septum. 19 Septa oblique, sloping towards apex on antisiphuncular side. Diagnosis. Suloceras with angle of expansion of 3 20 Siphuncle subcentral. Diameter of septal perforation 1.6 mm at degrees; cross-section circular; ornamented with alter- 21 cross-section diameter of 15 mm. Shape of siphuncular segments nating prominent and faint subordinate longitudinal li- 22 not preserved. Septal necks suborthochoanitic. Thin episeptal rae; more than 60 prominent longitudinal lirae around 23 deposits occur at most apical septa. circumference; longitudinal and transverse lirae vague; 24 undulations shallow; c. 4–5 undulations at distance sim- 25 Remarks. The closely spaced oblique septa and the subor- ilar to cross-section diameter; septal distances 0.4 of 26 thochoanitic septal necks allow assignment of this frag- cross-section diameter; sutures straight and slightly obli- 27 ment to Diagoceras. It displays a significantly higher angle que, sloping in adoral direction on prosiphuncular side; 28 of expansion (15 degrees) than Diagoceras aptum (Hall, septal necks suborthochoanitic; siphuncular segments 29 1876) in which it is 6 degrees. However, the single speci- nearly tubular with diameter between 0.15–0.2 of cross- 30 men is too poorly preserved and incomplete for specific section; width to height ratio of siphuncular segments 31 determination to be possble. 0.68. 32 33 Description. Holotype 39 mm long, cross-section diameter 14– 34 Genus SULOCERAS Manda, 2001 16 mm (angle of expansion 3 degrees). Cross-section circular. 35 First order longitudinal lirae 1.3 mm apart at adoral end of 36 Type species. Orthoceras pulchrum Barrande, 1866, from the holotype. Distances between directly transverse lirae c. 0.2 mm. 37 Kone´prusy Limestone, Pragian, of Bohemia, Czech Republic. Transverse and longitudinal lirae form square pattern (Pl. 7, fig. 38 10). Distance between shallow undulations 5 mm. Distance 39 Diagnosis (after Manda 2001, p. 277). Slender orthocones between two most adoral septa 6 mm. Septal perforation at most adoral septum 2.8 mm (0.18 of cross-section). Septal necks sub- 40 with undulating conch; cross-section circular; ornamented orthochoanitic; siphuncle subcentral. Siphuncular segments 41 with alternating prominent and faint subordinate longitu- dinal lirae, and faint directly transverse lirae; longitudinal slightly expanded within chambers or nearly tubular (Pl. 9, 42 fig. 5). and transverse lirae form rectangular ornament; at ephe- 43 Two additional specimens are poorly preserved fragments of 44 bic stage ornamented with differentiated longitudinal phragmocone. MB.C.9784 has angle of expansion of 4 degrees 45 striae of first to third order and faint growth lines; 3–5 and displays characteristic ornamentation consisting of undula- 46 septa at distance similar to cross-section diameter; sutures tions, numerous regularly spaced longitudinal lirae c. 0.5 mm 47 straight and slightly oblique; septal necks suborthochoan- apart, faint subordinate longitudinal lirae and faint straight, 48 itic; siphuncular segments slightly expanded; mural and transverse lirae. 49 episeptal deposits present. 50 Remarks. This species differs from S. pulchrum in having 51 Remarks. This genus differs from Spyroceras in having wider septal spacing and less conspicuous, smooth undu- 52 suborthocoanitic septal necks and a conspicuous orna- lations, and from S. melolineatum Niko, 1996, in having 53 mentation consisting of alternating prominent and subor- more widely spaced septa and undulations, and a wider 54 dinate longitudinal lirae. siphuncle. 52 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Order LITUITIDA Starobogatov, 1974 Genus ARTHROPHYLLUM Beyrich, 1850 2 Family LAMELLORTHOCERATIADE Teichert, 1961 3 Type species. Orthoceratites crassus Roemer, 1844, from the Wis- 4 Remarks. Kolebaba (1999) assigned Arthrophyllum Bey- senbach Slate, Eifelian, of Schalke, Harz Mountains, Germany. 5 rich, 1850 and the Lamellorthoceratidae together with 6 Plagiostomoceras and Protobactrites to the Pallioceratida Diagnosis (after Bandel and Stanley 1989, p. 411). Conch 7 Marek, 1998, an order erected on the assumption of straight with angle of expansion of 4–12 degrees; conch 8 the presence of a cameral (pallial) mantle. This charac- cross-section circular or slightly compressed; ornamented 9 ter is a physiological hypothesis. I do not consider that with fine transverse ornament or with costules; siphuncle 10 a taxon can be erected on such a basis, only on subcentral–eccentric; siphuncular segments tubular or 11 observed characters; hence, I do not regard the order slightly expanded within chambers; septal necks orthocho- 12 to be valid. In fact, the different genera that have been anitic; cameral deposits characterised by irregularly 13 assigned to the Pallioceratida display strong differences arranged straight to sinuous cameral lamellae, inclined 14 in conch morphology. Although Plagiostomoceras and longitudinally, which converge towards siphuncle. 15 Protobactrites are similar to lituitids in having a longi- 16 tudinal lamella, which is a diagnostic character of the Remarks. Lamellorthoceras Termier and Termier, 1950, was 17 Lituitida, they differ significantly in septal neck shape. regarded as synonymous with Arthrophyllum Beyrich, 1850, 18 The longitudinal lamella is considered homoeomorphic by Bandel and Stanley (1989). They demonstrated that 19 in a variety of orthocones with wide septal spacing. the differences in the shape of the endocameral lamella, 20 Flower (1939) described a longitudinal lamella in sev- which serve to distinguish between the two genera, are 21 eral pseudorthoceridans. Moreover, the typical cameral a product of fossilisation. Moreover, the conchs of 22 deposits that cover the septal necks in apical phragmo- Orthoceratites crassus and Lamellorthoceras vermiculare 23 cone parts of lituitids (termed ‘epichoanitic deposits’ (Termier and Termier, 1950) are similarly transversely 24 herein) do not occur in Plagiostomoceras and Protobac- ornamented. 25 trites. The latter is considered an exclusive character of 26 the Lituitida (Dzik 1984; Kro¨ger et al. 2008). The pres- Occurrence. Emsian–Eifelian; Armorican Massif (France), 27 ence of epichoanitic cameral deposits in Lamellorthoc- Morocco, New York State and Turkey. 28 eras is the main argument for assigning this genus and 29 the Lamellorthoceratidae to the Lituitida (Text-fig. 2). Arthrophyllum vermiculare (Termier and Termier, 1950) 30 In Sphooceras Flower, 1962 there are deposits that are Plate 7, figure 13; Plate 11, figures 1, 3–5; Text-figure 2 31 interpreted as epichoanitic (Text-fig. 16). Therefore, 32 Dzik’s (1984) opinion is followed herein and the *1950 Lamellorthoceras vermiculare Termier and Termier, 33 Sphooceratidae are assigned to the Lituitida. p. 41, pl. 135, figs 7–11. 34 35 36 37 EXPLANATION OF PLATE 7 38 Ornamentation of Early Devonian Lituitida, Orthocerida and Pseudorthocerida from the Filon Douze section. 39 Fig. 1. Subdoloceras atrouzense gen. et sp. nov., MB.C.9595, holotype; bed KMO-II, Pragian. 40 Fig. 2. Subdoloceras engeseri gen. et sp. nov., MB.C.9657; bed KMO-I, Pragian. 41 Fig. 3. Spyroceras latepatronus sp. nov., MB.C.9653, holotype; bed KMO-I, Pragian. 42 Fig. 4. Spyroceras cyrtopatronus sp. nov., MB.C.9649; bed KMO-I, Pragian. 43 Fig. 5. Geidoloceras ouaoufilalense gen. et sp. nov., MB.C.9627, holotype; bed KMO-III, Pragian. 44 Fig. 6. Spyroceras patronus (Barrande, 1866), MB.C.9652; bed KMO-I, Pragian. 45 Fig. 7. Spyroceras sp. A., MB.C.9698; bed KMO-III, Pragian. 46 Fig. 8. Spyroceras sp. B., MB.C.9699; bed KMO-III, Pragian. 47 Fig. 9. Spyroceras fukuijense? Niko, 1996, MB.C.9777; bed KMO-III, Pragian. 48 Fig. 10. Suloceras longipulchrum sp. nov., MB.C.9783, holotype; bed KMO-III, Pragian. 49 Fig. 11. Anaspyroceras sp., MB.C.9680; bed KMO-III, Pragian. 50 Fig. 12. Pseudospyroceras reticulum gen. et sp. nov., MB.C.9788, holotype; bed KMO-II, Pragian. 51 Fig. 13. Arthrophyllum vermiculare (Termier and Termier, 1950), MB.C.9648; bed KMO-V, Dalejian, Emsian. 52 Fig. 14. Reticuloceras loricatum (Barrande, 1868), MB.C.9646; bed KMO-II, Pragian. 53 Fig. 15. Angeisonoceras reteornatum gen. et sp. nov., MB.C.10092, bed KMO-II, Pragian. 54 All ·5. PLATE 7 1 2 3 4 5 6 7 8 1 9 10 11 2 3 4 12 13 14 15 16 17 18 19 20 21 22 23 24 25 5 6 7 26 27 28 29 30 31 32 33 34 35 36 37 38 39 8 9 10 11 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 12 13 14 15 KRO¨ GER, Lituitida, Orthocerida, Pseudorthocerida 54 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 1950 Lamellorthoceras gracile Termier and Termier, p. 41, Largest known fragment has diameter of 44 mm (MB.C.9585) 2 pl. 137, figs 5–6. with two chambers 13 mm (adoral chamber) and 14 mm (ad- 3 1966 Arthrophyllum vermiculare (Termier and Termier); apical chamber) in length. MB.C.9648 slightly bent, 137 mm 4 Babin, pp. 337–340, pl. 15, figs 1–8. long, cross-section diameter of 24–41 mm. Fragment has 17 5 1966 Arthrophyllum gracile? (Termier and Termier); complete chambers; length of most adoral chamber 9.6 mm, Babin, p. 340, pl. 15, fig. 9. most adapical 6 mm. Depth of curvature of most adapical 6 1976 Lamellorthoceras vermiculare Termier and Termier; chamber 7 mm. Septal perforation of most adapical septum 7 Stanley and Teichert, pl. 1, figs 10–11, pl. 2, figs 2–3. 2.9 mm wide. Centre of septal perforation positioned 11.2 mm 8 1976 Lamellorthoceras gracile Termier and Termier; from conch margin. Septal necks orthochoanitic, slightly bent 9 Stanley and Teichert, pl. 1, fig. 12. outward, deviating from direction of growth, forming slight con- 10 1984 Lamellorthoceras gracile Termier and Termier; Dzik, striction of siphuncular tube at septal perforation. Length of sep- 11 p. 138, text-fig. 55.31. tal neck of second most adapical septum 0.7 mm. Siphuncular 12 2008 Lamellorthoceras vermiculare Termier and Termier; tube slightly expanded within chambers with maximum diameter 13 Klug et al., p. 41, pl. 5, figs 3–7, pl. 6, figs 17–18. close to adoral end of each segment (Pl. 11, figs 3–5). Adapical 14 septal necks covered with 0.2-mm-thick epichoanitic deposits 15 Material. 266 specimens from beds OJ-I, MB.C.7576.1–15, (Pl. 11, fig. 3). Siphuncular tube of entire specimen covered by 16 KMO-I, MB.C.9578.1–10, 9578, 9693, 9752.1–11, 9753–54, lamellar cameral deposits. Lamellar epi- and hyposeptal deposits fill entire chambers between siphuncle and conch margin on 17 9756–57, 9789–99, KMO-II, MB.C.9781–82, 9762.1–55, KMO- III, MB.C.9525, 9765.1–13, KMO-IV, MB.C.9770.1–4, KMO–V, prosiphuncular side. MB.C.9693 shows that longitudinal lamellae 18 MB.C.9648, Erbenoceras Limestone, MB.C.9573, 9574.1–3, and of cameral deposits are irregularly bent, sometimes bifurcate and 19 F, MB.C.9572; and 6 specimens from EF, MB.C.9766.1–6; Loch- merge together or are folded (Pl. 11, fig. 1). 20 kovian–Eifelian, Filon Douze section. 21 Remarks. The species diagnosis given above is based on 22 Emended diagnosis. Conch straight or very slightly bent, the original figures of Termier and Termier (1950, pl. 23 with angle of expansion below 12 degrees, most speci- 135, figs 7–11; pl. 137, figs 5–6) and the material 24 mens with angle of expansion of c. 6 degrees; cross-sec- described here. 25 tion circular or compressed with average width to height Termier and Termier (1950) erected two species of 26 ratio of 0.9; ornamented with fine, acutely raised lirae; li- Lamellorthoceras; a small species with short septal distance 27 rae oblique, sloping adapically, forming broad lobe on (L. gracile) and a large species with a higher expansion 28 prosiphuncular side of conch, straight on lateral sides; rate and wider septal spacing (L. vermiculare). The mate- 29 sutures straight; septal distance 0.2–0.45, but in most rial from the Filon Douze section reveals that these two 30 specimens c. 0.25 of cross-section; septal perforation sub- species in fact represent two growth stages of the same 31 central; margin of septal perforation positioned at conch species. The variability of conch cross-section, septal spac- 32 cross-section centre; diameter of septal perforation c. 0.1 ing and angle of expansion is considerable in the speci- 33 of conch cross-section; siphuncular segments slightly mens measured (Text-fig. 19), but does not allow for the 34 expanded within chambers; septal necks orthochoanitic; recognition of more species. Epichoanitic deposits in 35 endosiphuncular deposits not known; epichoanitic, epi-, specimens MB.C.9648, 9789–99 and 9697–98 indicate that 36 and hyposeptal deposits present; cameral deposits form the species must be assigned to the Lituitida. Arthrophyl- 37 irregularly arranged radial lamellae; endocameral deposits 38 apically cover connecting ring. n 39 25 ntotal=91 40 Description. Conch straight, sometimes very slightly cyrtoconic 41 with siphuncle at convex side of curvature of growth axis. 20 42 Angle of expansion between 4 and 12 degrees, average of 91 43 fragments 5.7 degrees (Text-fig. 14). Cross-section circular or 15 44 compressed, average width to height ratio of conch-cross-sec- tion of 91 fragments 0.87, standard deviation 0.08 (see Text- 45 10 46 fig. 15). Shell ornamented with obliquely transverse, acute lirae 47 (Pl. 7, fig. 13). Distance between lirae small, in MB.C.9648 0.3 mm at cross-section of 34 mm, in MB.C.9697 0.2 mm at 5 48 cross-section of 10 mm. Ridges slope at an angle of c.10 49 degrees towards dorsoventral axis, sloping adapically in prosip- 50 huncular direction. Sutures straight and directly transverse at 1.1 3.4 4.6 6.8 9.1 11.3 apical angle in degrees 51 distances of 0.2 (adoral chambers of MB.C.9697) to 0.4 52 (adoral chambers of MB.C.9789) of conch cross-section. Most TEXT-FIG. 14. Frequency distribution of angle of expansion 53 fragments have septal distances of about one-quarter of cross- of 91 specimens of Arthrophyllum vermiculare from Filon Douze. 54 section. A clear single frequency peak occurs at c. 5 degrees. 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 55

1 45 Remarks. The generic diagnosis follows Sweet (1964b), 2 who noted however: ‘Neither cameral nor siphuncular 3 n=93 deposits reported’. The specimens from Filon Douze exhi- 4 bit endocameral deposits, which are, therefore, included 5 in the diagnosis.

6 5.7 7 Occurrence. Late Silurian; Carnic Alps (Austria), Czech Republic, 8 Morocco, Sardinia, UK and Ukraine. 9 10 angle of expansion in degrees 11 Sphooceras truncatum (Barrande, 1860) 12 0.06 Plate 6, figure 2; Plate 11, figure 2; Text-figure 16 1 10 100 13 conch cross section diameter in mm 14 *1860–74 Orthoceras truncatum Barrande, pp. 556–559, 15 TEXT-FIG. 15. Angle of expansion and average cross section 573–600, pl. 9, figs 1–20; pl. 342, figs 1–20; pl. 344, 16 diameter of 93 fragments of Arthrophyllum vermiculare.No figs 1–6; pl. 448, figs 3–5. correlation is visible; axes are scaled logarithmically. 1883 Orthoceras truncatum Barrande; Gaudry, p. 153, 17 text-fig. 131. 18 lum vermiculare is the most common nautiloid in bed 1925 Orthoceras truncatum Barrand; Heller, p. 245, pl. 3, 19 OJ-II and the Pragian marls and limestones. fig. 19. 20 1962 Sphooceras truncatum (Barrande); Flower, p. 95. 21 Occurrence. Lochkovian–Eifelian; France and Morocco. 1964 Sphooceras truncatum (Barrande); Sweet, K231, 22 fig. 156A5. 23 1975 Sphooceras truncatum (Barrande); Balashov, 24 Family SPHOOCERATIDAE Flower, 1962 pp. 81–85, pl. 3, fig. 5. 25 1984 Sphooceras truncatum (Barrande); Dzik, pp.112, 135, 26 Remarks. Dzik (1984) assigned Sphooceras Flower, 1962, to 138, pl. 31, figs 5–7, text-figs 42.19, 55.35. 27 the Lituitida, although diagnostic characters of this group, 1986 Sphooceras truncatum (Barrande); Turek and Marek, pp. 250, 252, figs 3–9. 28 such as a longitudinal lamellae and epichoanitic deposits, 1987 Sphooceras truncatum (Barrande); Kiselev, Mironoya 29 had not been described in the genus. The specimens of and Sinitsina, p. 50, pl. 13, fig. 4. 30 Sphooceras from Filon Douze are not well preserved, but in 1990 Sphooceras truncatum (Barrande); Gnoli, pp. 302, 31 some cases show endocameral deposits that entirely cover 304, pl. 4, figs 2–5. 32 septal necks (Pl. 11, fig. 2; Text-fig. 16). Because of the poor 1991 Sphooceras truncatum (Barrande); Gnoli and 33 preservation, the possibility that these deposits were precip- Serpagli, p. 188, 194, pl.1, fig. 7. 34 itated post-mortem cannot be dismissed. The assignation 1994 Sphooceras truncatum (Barrande); Gnoli and Kiselev, 35 of the Spooceratidae to the Lituitida must remain question- p. 416, text-fig. 1a–c. 36 able until better preserved material becomes available. 1999 Sphooceras truncatum (Barrande); Histon and Gnoli, 37 pp. 384, 388, tables1–2. 38 Material. 5 specimens, MB.C.9702–04, 9801–02, from bed OP- 39 Genus SPHOOCERAS Flower, 1962 M; 1 specimen, MB.C.9301, from nodules in OP-M, Ludfordian, 40 Filon Douze section. 41 Type species. Orthoceras truncatum Barrande, 1860, from the 42 upper Silurian of Bohemia, Czech Republic. Diagnosis. Sphooceras with conch cross-section at position 43 of septum of truncation of c. 10–20 mm; cross-section ellip- 44 Emended diagnosis. Gradually expanding orthocones with tically compressed; septa closely spaced, c. 0.3 of cross-sec- 45 subcentral orthochoanitic siphuncle and long chambers tion; sutures oblique, sloping in adapical direction on 46 separated by conical septa; at apical end of all known prosiphuncular side of conch; siphuncle markedly eccentric. 47 specimens three-layered conical callus occurs, sealing sip- huncular termination and smoothing contour of shell; 48 Description. Septum of truncation of five specimens at cross-sec- inner layer of callus smooth; intermediate layer marked 49 tion 10–14 mm. Cross-section elliptically compressed with width by striae that radiate outward from apex; outer layer 50 to height ratio of 0.78–0.85. Three specimens have three cham- 51 ornamented with concentric striae broken on opposite bers adoral of septum of truncation; two have four chambers 52 sides of conch by lines of V-shaped invaginations in indi- adoral of chamber of truncation. Septal distance invariably c. 0.3 53 vidual striae; deciduous portion of conch not known; Epi- of height of conch cross-section. Diameter of septal perforation 54 choanitic and epi- and hyposeptal deposits occur. 0.17 of conch height. Septal necks orthochoanitic, 0.5 mm long, 56 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 mature body chamber decreases towards aperture; adult 2 cross-section diameter about 2 mm; cross-section slightly 3 depressed or circular with flattened prosiphuncular side; 4 ornamented with smooth undulations, sloping adapically 5 on prosiphuncular side; undulations form conspicuous 6 sharp lobe on prosiphuncular side and rounded saddle on 7 antisiphuncular side; sutures straight with shallow lobes on 8 prosiphuncular side in adolescent growth stages; at position 9 where cross-section diameter reaches its maximum, septal 10 distance abruptly decreases and four closely spaced sutures 11 form wide conspicuous saddles on prosiphuncular side; 12 most adoral of four lobate sutures less curved and compen- 13 sate for following straight adoral septa; following septa 14 nearly straight, forming faint saddle on prosiphuncular 15 side; septal spacing in adolescent growth stages c. 0.4 of 16 conch cross-section, of lobate septa 0.12–0.2 of conch cameral deposits 1 mm 17 cross-section, of latest septa 0.3; septal curvature shallow; 18 TEXT-FIG. 16. Camera lucida drawing of epichoanitic septal necks orthochoanitic; septal perforations with diam- 19 deposits in median section of Sphooceras truncatum; MB.C.9702, eter 0.16 of conch cross-section; siphuncle position eccen- Ludlow, Filon Douze. 20 tric; endosiphuncular and cameral deposits unknown. 21 22 23 one-quarter of septal perforation, one-eighth of chamber height. Chebbioceras erfoudense Klug et al., 2008 24 Most apical septa and septal necks covered with epichoanitic Text-figure 17A–G 25 and hypocameral deposits that entirely cover septal necks. 26 Deposits differ from bluish-grey sparitic chamber fillings in con- 2005 Bactrites sp. B; Kro¨ger et al., p. 333, pl. 4C. sisting of fine yellowish, radially arranged crystals of calcite 27 * 2008 Chebbioceras erfoudense Klug et al. pp. 42–43, pl. 5, (Text-fig. 16; Pl. 11, fig. 2). 28 figs 16–18. 29 Remarks. This species was described in detail by Barrande 30 Material. 10 fragments, MB.C.9624–25, 10194, 10198–204, from (1860–74) and several subsequent authors so it is not nec- ´ 31 bed EF, Zlıchovian, Emsian, Filon Douze section. essary to provide yet another full description. A detailed 32 description of the cameral deposits requires better pre- Diagnosis. As for genus. 33 served material. Sphooceras truncatum differs from 34 S. amplum Kiselev, in Balashov and Kiselev 1968 in being Description. MB.C.10199 nearly identical to holotype (see Text- 35 smaller at the point of truncation, and in having a more fig. 17A–B), maximum cross-section 2 mm in diameter, length 36 eccentrically positioned siphuncle and closer septal spacing. 2.9 mm, five chambers preserved, similar sutural pattern and 37 dimensions. Several specimens are fragments of phragmocone with 38 Occurrence. Wenlock–Lochkovian; Carnic Alps (Austria), Czech diameter of 1.3–1.6 mm and angle of expansion of 16–17 degrees, 39 Republic, Germany, Sardinia and UK. showing characteristic ornamentation. MB.C.10198 1.0 mm long 40 with two chambers 0.5 mm high. Adapical diameter of specimen 41 1.3 mm, adoral diameter 1.6 mm. Siphuncular perforation of adoral septum 0.2 mm wide. Centre of septal perforation posi- 42 Order ORTHOCERATIDA Kuhn, 1940 tioned 0.5 mm from conch margin. MB.C.10198 has orthochoanit- 43 Family ORTHOCERATIDAE McCoy 1844 44 ic septal necks (Text-fig. 17F). Largest specimen, MB.C.10201, with 45 cross-section diameter of 2.2 mm and at adapical end displays one Genus CHEBBIOCERAS Klug et al., 2008 chamber 0.2 mm high. Adoral part of chamber preserved. 46 47 Type species. Chebbioceras erfoudense Klug et al., 2008, from the 48 lower Emsian of Ouidane Chebbi, Tafilalt, Morocco. Genus INFUNDIBULOCERAS Klug et al., 2008 49 50 Other species included. None. Type species. Bogoslovskya mira Zhuravleva, 1978, from the 51 Famennian of Verchi, South Ural Mountains, Russia (species 52 Diagnosis. Small straight orthocones with angle of expan- combined with Infundibuloceras below: see ‘List of new combina- 53 sion in adolescent growth stages of c. 17 degrees; at last sep- tions’). 54 tum of mature specimen nearly tubular; cross-section of 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 57

1 Diagnosis. Slender, straight conch with nearly circular choanitic, forming funnel that opens gradually at adoral and ad- 2 cross-section; surface smooth or faintly ornamented; angle apical end. Narrowest point of septal perforation at adoral third 3 of expansion below 5 degrees; sutures straight, transverse; of length of septal necks. Septal neck length of most adoral 4 septal distance wide, more than 0.5 of conch cross- septum 5 mm. 5 section; siphuncle central–eccentric; septal perforation 6 narrow, below 0.1 of cross-section; septal necks orthocho- Remarks. Infundibuloceras brevimira differs from Bogo- 7 anitic and form funnel that opens gradually at adoral and slovskya mira Zhuravleva, 1978 in having shorter sep- 8 adapical end; length of septal necks considerably exceeds tal necks and a lower expansion rate; the septal 9 diameter of septal perforation; no cameral or endosiphun- necks of B. mira are one-half of the septal distance in 10 cular deposits. length. 11 12 Other species included. Infundibuloceras brevimira Klug et al., 13 2008; I. longicameratum sp. nov.; I. mohamadii sp. nov.; Infundibuloceras longicameratum sp. nov. 14 Sinoceras komiense Zhuravleva, 1978 (species combined with Plate 12, figure 5 15 Infundibuloceras below: see ‘List of new combinations’). 16 Derivation of name. Latin, longus, long, referring to the wide septal spacing of this species. 17 Remarks. Infundibuloceras differs from Bogoslovskya 18 Zhuravleva, 1978, in having very long septal necks that Holotype. MB.C.9705 (Pl. 12, fig. 5). 19 open funnel-like adorally and adapically; the septal spac- 20 ing also tends to be wider. Tibichoanoceras gen. nov. is similar in general conch shape and also displays very Type locality and horizon. Filon Douze section; bed PI, early O. 21 costatus conodont Biozone, early Eifelian. 22 long septal necks; it differs in having straight septal necks that form a strictly tubular septal perforation 23 Other material. 1 specimen, MB.C.9696, from bed KMO-IV, (Text-fig. 18D). Infundibuloceras differs from Michelinoc- 24 Zlı´chovian, Emsian, Filon Douze section. 25 eras in having an eccentric siphuncle (compare Text- fig. 18A, C). 26 Diagnosis. Infundibuloceras with angle of expansion below 27 3 degrees; sutures straight transverse; septal distance wide, Occurrence. Emsian–Famennian; Morocco and Russia. 28 c. 1.5 of conch cross-section; siphuncle eccentric; septal 29 perforation narrow, 0.05 of cross-section; length of septal 30 necks 0.2 of cameral length, approximately twice diameter Infundibuloceras brevimira Klug et al., 2008 31 of septal perforation. Plate 9, figure 11; Text-figure 18C 32 33 Description. Holotype 79 mm long, cross-section diameter 15– * 2008 Infundibuloceras brevimira Klug et al. pp. 43–44, 34 19 mm (angle of expansion 2.9 degrees). Shell surface not pre- pl. 5, figs 10–12. 35 served. Sutures directly transverse. Holotype has three septa at 36 distances measured from adoral to adapical end of 30, 27 and Material. 5 specimens, MB.C.10071–76, from bed EF; 2 speci- 22 mm. Septal perforation at most adapical septum 6 mm from 37 mens, MB.C.9792–93, from bed KMO-IV, Zlı´chovian, Emsian, 38 conch margin where conch cross-section is 16.2 mm. Minimum Filon Douze section. diameter of septal perforation 0.7 mm at most apical septum. 39 Septal necks orthochoanitic, form funnel that opens gradually at 40 Diagnosis. Infundibuloceras with angle of expansion below adoral and adapical ends. Narrowest point of septal perforation 41 3 degrees; sutures straight, transverse; septal distance at adapical third of length of septal necks. Septal neck of most 42 wide, approximately same as conch cross-section diame- apical septum 3.9 mm long. 43 ter; siphuncle eccentric; septal perforation narrow, 0.09 of 44 diameter of conch cross-section; length of septal necks 0.2 Remarks. Infundibuloceras longicameratum differs from 45 of cameral length, more than three times diameter of sep- Bogoslovskya mira Zhuravleva, 1978 in having shorter sep- 46 tal perforation. tal necks and a lower expansion rate, and from I. brevi- 47 mira in having significantly wider septal spacing and 48 Description. Holotype 76 mm long, cross-section diameter 21– differently shaped septal necks. Its septal perforations are 49 24 mm (angle of expansion 2.6 degrees). Shell surface not pre- narrowest close to the distal tip of the septal necks, 50 served. Sutures directly transverse. Holotype has three complete whereas those of I. brevimira are narrowest close to the 51 septa at distances measured from adoral to adapical end of 25.5, adoral part of the necks; Sinoceras komiense Zhuravleva, 52 24.0 and 21 mm. Septal perforation positioned at most adapical 1978 differs in having septal necks 0.4–0.6 of the length septum 8 mm from conch margin. Minimum diameter of septal 53 of the chambers. 54 perforation 1.7 mm at most adoral septum. Septal necks ortho- 58 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Infundibuloceras mohamadi sp. nov. Additional specimens are poorly preserved phragmocone frag- 2 Plate 9, figure 6 ments. One larger specimen (MB.C.9688) displays septal spacing 3 0.7 of cross-section diameter at conch cross-section diameter of 4 Derivation of name. In honour of Mohamad, elder son of Filon 15 mm. Smaller specimen (MB.C.9689) with cross-section diam- 5 Douze miner Lahcan Caraoui. eter of 6–10 mm. Septal spacing of this fragment is significantly wider, being 0.8–0.9 of cross-section diameter. 6 7 Holotype. MB.C.9687 (Pl. 9, fig. 6). Remarks. Infundibuloceras mohamadi differs from species 8 of Bogoslovskya in having longer septal necks in combina- 9 Type locality and horizon. Filon Douze section, Erbenoceras Limestone, Zlı´chovian, Emsian. tion with a large siphuncular diameter. It differs from 10 Bogoslovskya mira Zhuravleva, 1978 in having shorter sep- 11 Other material. 3 specimens, MB.C.9688–90, from the type tal necks and a greater siphuncular diameter. 12 locality and horizon. 13 14 Diagnosis. Straight, slender orthocones with angle of Genus KOPANINOCERAS Kiselev, 1969 15 expansion of 4 degrees; cross-section circular; shell surface 16 smooth; septal distance 0.6 of cross-section diameter; Type species. Orthoceras jucundum Barrande, 1870, from the 17 sutures straight and directly transverse; septal perforation Ludlow of Dvoretz, Bohemia, Czech Republic. 18 between centre and conch margin; septal curvature shallow; 19 septal necks orthochoanitic; length of septal neck c. 0.25 of Diagnosis (after Zhuravleva 1978, p. 53). Orthocones or 20 chamber length, similar to diameter of septal perforation; very slightly cyrtocones with circular or slightly depressed 21 diameter of septal perforation 0.1 of conch cross-section. cross-section; ornamented with distinct growth lines; 22 sutures straight; siphuncle central–eccentric with cylindri- 23 Description. Holotype with smooth surface, 100 mm long, circu- cal segments; septal necks funnel-like with shell thicken- 24 lar cross-section with diameter of 15–22 mm (angle of expansion ing near distal end of necks, forming constriction of 25 4 degrees). Distance between two most adoral septa 10 mm, septal perforation close to tips of septal necks; endosip- 26 between two most adapical septa 9.6 mm. Septal concavity with huncular and cameral deposits unknown. 27 depth of curvature of 6 mm at most adoral septum. Septal per- foration at most adoral septum 2.2 mm (0.1 of cross-section). 28 Remarks. Kopaninoceras differs from Bogoslovskya and In- 29 Septal necks orthochoanitic. Length of septal necks at most adoral septum 2.1 mm. Siphuncle position eccentric, c. 7mm fundibuloceras in having a nearly central to slightly eccen- 30 tric siphuncle; the septal necks are unique in shape, 31 from conch margin at adoral end of specimen. 32 33 34 35 EXPLANATION OF PLATE 8 36 Median sections of Pseudorthocerida from the Filon Douze section. 37 Fig. 1. Subdoloceras atrouzense gen. et sp. nov., MB.C.9595, holotype; bed KMO-II, Pragian; detail of septal perforation showing 38 cyrtochoanitic septal necks. 39 Fig. 2. Reticuloceras loricatum (Barrande, 1868), MB.C.9686; bed KMO-II, Pragian; fragment with suborthochoanitic septal necks. 40 Fig. 3. Subdoloceras tafilaltense gen. et sp. nov., MB.C.9695, holotype; bed KMO-IV, Daleijan, Emsian; note the suborthochoanitic 41 septal necks and the slightly expanded siphuncular segments. 42 Fig. 4. Probatoceras?sp., MB.C.9651; bed KMO-II, Pragian; note the angular suborthochoanitic septal necks. 43 Fig. 5. Geidoloceras ouaoufilalense gen. et sp. nov., MB.C.9627, holotype; bed KMO-III, Pragian; detail of septal perforation showing 44 cyrtochoanitic septal necks and expanded siphuncular segments. 45 Fig. 6. Subormoceras erfoudense gen. et sp. nov., MB.C.9686, holotype; Erbenoceras Limestone, Zlı´chovian, Emsian; detail of septal 46 perforation; note the rounded suborthochoanitic septal necks. 47 Fig. 7. Subdoloceras engeseri gen. et sp. nov., MB.C.9654, holotype; bed KMO-I, Pragian; note the suborthochoanitic septal necks. 48 Figs 8, 11. Spyroceras cyrtopatronus sp. nov., MB.C.9676, holotype; bed KMO-III, Pragian. 8, section showing cameral deposits and 49 cyrtochoanitic septal necks. 11, detail of septal perforation showing cyrtochoanitic septal necks and expanded siphuncular 50 segments. 51 Fig. 9. Subormoceras rissaniense gen. et sp. nov., MB.C.9678, holotype; bed F, P. partitus conodont Biozone, Eifelian; section showing 52 angular suborthochoanitic septal necks and elliptically expanded siphuncular segments. Scale bar represents 10 mm. 53 Fig. 10. Subormoceras sp., MB.C.9674; bed OSP-I, Prˇidolian, detail of the septal perforation with suborthochoanitic septal necks. 54 Scale bars represent 1 mm except where indicated. PLATE 8 1 2 3 4 5 6 7 8 9 10 11 12 13 1 14 15 2 16 17 18 19 20 21 22 23 24 25 3 26 27 28 29 4 30 31 5 32 33 34 35 36 37 38 39 40 41 6 42 43 44 45 46 47 48 78 49 50 51 52 53 9 10 11 54 KRO¨ GER, Pseudorthocerida 60 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 1977 Kopaninoceras jucundum (Barrande); Serpagli and 2 Gnoli, p. 160, pl. 1, fig. 1a–b, text-fig. 3. 3 1982 Kopaninoceras jucundum (Barande); Kiselev and 4 Evseev, p. 110. 5 1984 Kopaninoceras jucundum (Barande); Dzik, pp. 97, 105, pl. 25, fig. 10, text-fig. 39.23. 6 1999 Kopaninoceras jucundum (Barande); Histon and 7 Gnoli, pp. 384, 388, tables 1–2. 8 9 Material. 2 specimens, MB.C.9526, 10085, from bed OJ-I, Loch- 10 kovian, Filon Douze section. 11 12 A B Diagnosis (after Serpagli and Gnoli 1977, p. 160). Kopan- 13 inoceras with circular cross-section; angle of expansion <8 14 degrees; ornamented with fine transverse lirae, slightly obli- 15 que towards growth axis, approximately ten lirae per 1 mm; 16 D septal spacing 0.6 of conch cross-section; concavity of septa 17 about one-third of chamber length; siphuncle central; septal C 18 perforation about one-tenth of conch cross-section; septal 19 necks orthochoanitic with length slightly more than dia- 20 meter of septal perforation; siphuncular segments tubular. 21 22 F Description. MB.C.9526 11 mm long, circular cross-section with 23 E diameter of 19–21 mm, angle of expansion 11 degrees. Two 24 complete chambers preserved; length of adapical chamber 25 9.3 mm, of adoral chamber 10.7 mm. Septal perforation of G 26 adapical septum 1.4–1.8 mm wide. Septal necks orthochoanitic, c. 2 mm long. Septal perforation central. 27 TEXT-FIG. 17. Chebbioceras erfoudense from the early MB. C.10085 17.6 mm long, minimum diameter 15 mm, angle 28 Zlı´chovian of Filon Douze. A–C, PIMUZ 7271, holotype, of expansion 8 degrees. Two complete chambers preserved; length 29 showing characteristic lobe pattern. A, lateral view. B, of adapical chamber 8.6 mm. Septal perforation of adapical sep- prosiphuncular view, showing characteristic angular lobe of 30 tum c. 1.4 mm in diameter. Septal necks orthochoanitic, length c. ornamentation. C, adapical view. D, MB.C.10201, adult body 31 1.8 mm, have shell thickening and minimum diameter of central chamber. E, MB.C.10200, adult body chamber, ventral view. F, 32 septal perforation close to adapical tip of neck (Pl. 9, fig. 7). specimen MB.C.10198, median section, showing orthochoanitic 33 septal necks. G, MB.C.10194, fragment of two juvenile 34 chambers, lateral view; note the large angle of expansion. All Remarks. The fragments described above are questionably 35 specimens ·15. assigned to K. jucundum because the diagnostically impor- 36 tant characters of the outer shell are not preserved. The forming a funnel with a constriction close to the distal 37 angle of expansion of both fragments is higher than that (adapical) tip of the neck (Text-fig. 18B). 38 known from the type material; however, the angle of 39 Occurrence. Ludlow–Early Devonian; Carnic Alps (Austria), expansion in K. thyrsus (Barrande, 1870) varies consider- 40 Czech Republic, France, Morocco, Sardinia and Ural Mountains ably between 4 and 11 degrees (see below) which, if a simi- 41 (Russia). lar variability for K. jucundum is assumed, the fragments 42 may reflect intraspecific variation. However, more material 43 is needed to evaluate the variability of this species. 44 Kopaninoceras? jucundum (Barrande, 1870) 45 Plate 9, figure 7, Plate 15, figure 5; Text-figure 18B Occurrence. Lower Silurian–Lochkovian?; Czech Republic, 46 Morocco, Northern Urals (Russia) and Sardinia. 47 *1870 Orthoceras jucundum Barrande, p. 518, pl. 380, 48 figs 4–7; pl. 409, figs 3–10. 49 1970 Kopaninoceras jucundum (Barrande); Barskov and Kopaninoceras? dorsatoides sp. nov. 50 Kiselev, p. 67, pl. 3, fig. 2. Plate 9, figure 10 51 1973 Kopaninoceras jucundum (Barrande); Kiselev, p. 125, 52 fig. 1a–c. Derivation of name. Latin, dorsum, back, lower or outer side, 53 1975 Kopaninoceras jucundum (Barrande); Chen, p. 282, referring to the similarity of this species with Kopaninoceras 54 pl. 4, figs 3–4, 7. dorsatum (Barrande, 1868). 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 61

1 Holotype. MB.C.9700 (Pl. 9, fig. 10). 1982 Michelinoceras thyrsus (Barrande); Kiselev and 2 Evseev, p. 110. 3 Type locality and horizon. Filon Douze section, bed OP-M, Lud- 1991 Kopaninoceras? thyrsus (Barrande); Gnoli and 4 fordian. Serpagli, pp. 190, 194, pl. 3, figs 4–5. 5 1999 Kopaninoceras thyrsus (Barrande); Histon and Gnoli, pp. 384, 388, tables 1–2, fig. 4C. 6 Other material. 77 fragments, MB.C.9750.1–31, 9705.1–43, from 7 the type locality and horizon. Material. 80 fragments, MB.C.9540–41, 9803, 10130, 10136.1– 8 Diagnosis. Kopaninoceras? with ovate, compressed cross- 36, 10137.1–39, 10180, from bed OP-M and limestone nodules 9 section; ratio of cross-section width to height 0.88; angle in OP-M, Ludfordian, Ludlow; 2 specimens, MB.C.9527–9528, 10 ˇ´ ´ of expansion c. 5 degrees; concavity of septa approxi- from bed OSP-I, Prıdolı; Filon Douze section. 11 mately one-third of chamber length; siphuncle subcentral; 12 Diagnosis (after Serpagli and Gnoli 1977, p. 161). Kopan- diameter of septal perforation about one-tenth of conch 13 inoceras with circular cross-section; septal spacing with 1– cross-section; septal necks orthochoanitic, length about 14 2 chambers at distance similar to cross-section diameter; 1.5 diameter of septal perforation, or less. 15 angle of expansion <4 degrees; concavity of septa approx- 16 Description. Holotype 41 mm long, cross-section diameter 9– imately one-third of chamber length; siphuncle eccentric, 17 13.5 mm (angle of expansion 6.3 degrees). Conch cross-section slightly more than its own diameter removed from conch 18 ovate with antisiphuncular side slightly narrower than prosip- centre; diameter of septal perforation about one-tenth of 19 huncular side. Average of angle of expansion of 78 specimens conch cross-section; septal necks orthochoanitic, length 20 4.6 degrees (range 1–10 degrees, standard deviation 2.3 degrees). about 1.5 diameter of septal perforation; thin episeptal 21 Septal spacing about 1.2 of conch cross-section in juvenile deposits at apical parts of phragmocone. 22 growth stages and 0.6 in later growth stages, can vary strongly 23 within one specimen; in holotype from most adoral to most Description. Conch circular in cross-section. Average of angle of 24 adapical chamber: 13.2, 10.8, 7.5 and 9.9 mm. Average septal expansion of 83 specimens 3.8 degrees (standard deviation 1.7 25 spacing c. 0.8 of conch cross-section. degrees; maximum 11 degrees, minimum 1 degree). Septal spac- 26 Curvature of most adoral septum of holotype 3.6 mm deep. ing can vary between 1.2 of conch cross-section diameter in 27 Septal perforation of most adoral septum 6.3 mm from conch juvenile growth stages and 0.4 in most adoral chambers of frag- margin; of second septum from adoral end 0.8–1 mm in diame- 28 ments of adult specimens. Average septal spacing c. 0.8 of conch ter. Septal necks orthochoanitic, 1.6 mm long, form funnel with 29 cross-section. minimum diameter of septal perforation close to adapical tip of MB.C.9803 has two chambers; length of adapical chamber 30 neck. 9 mm, of adoral chamber 12 mm. Conch cross-section at med- 31 ian septum 16 mm where septal perforation is 1.3–1.1 mm; sep- 32 Remarks. The fragments described above are questionably tal necks orthochoanitic, 1.8 mm long, form funnel with 33 assigned to Kopanicoceras because the diagnostically minimum diameter of septal perforation close to adapical tip of 34 important characters of the outer shell are not preserved. neck. Centre of septal perforation of median septum 7.5 mm 35 Kopaninoceras? dorsatoides is similar to K. dorsatum in from conch margin. MB.C.10130 has three chambers 9.4 (adapi- 36 having a compressed ovate cross-section and an eccentric cal), 10.6 (middle), and 10.3 (adoral) mm long. Conch cross- 37 siphuncle, but differs in having a lower expansion rate section 16–19 mm; at adoral septum, septal perforation 1.7– 1.4 mm wide; septal necks orthochoanitic, 1.8 mm long, form 38 and shorter septal necks. 39 funnel with minimum diameter of septal perforation close to ad- 40 apical tip of neck. Centre of septal perforation of adoral septum 7.5 mm from conch margin. 41 Kopaninoceras thyrsus (Barrande, 1870) 42 Plate 9, figure 9 Remarks. Kopaninoceras thyrsus is distinguished from 43 other species of the genus in having a combination of low 44 * 1870 Orthoceras thyrsus Barrande, p. 555, pl. 405, expansion rate, a circular cross-section and an eccentric 45 figs 15–18. siphuncular position. It differs from K. dorsatum in hav- 46 non 1960 Orthoceras? thyrsus Barrande; Lai, pp. 258, 269: ing a low expansion rate and a circular cross-section, and 47 pl. 2, fig. 7a–c. from K. jucundum in having a more eccentric siphuncle 48 1968 Michelinoceras sp. A; Ristedt; pl. 1, fig. 4a [fide and a lower conch expansion rate. 49 Kiselev 1972]. The material shows that a high variability of septal 50 1972 Michelinoceras thyrsus (Barrande); Kiselev, p. 427. spacing exists within this species; it can vary between 0.4 51 1977 Kopaninoceras? thyrsus (Barrande); Serpagli and Gnoli, p. 161, pl. 1, fig. 4a–b. and 1.2 of conch cross-section even within a single speci- 52 1979 Kopaninoceras? thyrsus (Barrande); Gnoli et al., men. Therefore, the diagnostic value of chamber height is 53 p. 418, table 4. limited in this species. 54 62 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Occurrence. Lower Silurian–Prˇı´dolı´; Czech Republic, Morocco, subcentral tubular siphuncle and a general conch shape 2 Northern Urals (Russia) and Sardinia. similar to that of Michelinoceras sp. A. of Ristedt (1968, 3 pl. 1, figs 3–4a), which was synonymized with K. thyrsus 4 by Gnoli and Serpagli (1977). The fragments differ in 5 Kopaninoceras? sp. having a cross-section diameter that is twice that of Rist- 6 Plate 13, figures 11–12 edt’s species. In bed OP-M fragments of Kopaninoceras 7 several centimetres long are most common beneath apical 8 Material. 3 apical fragments, MB.C.10079–81, from limestone fragments of Arionoceras, which are also very common in 9 nodules in bed OP-M, Ludfordian, Filon Douze section. this bed. Hence, although the apices described probably 10 represent Kopaninoceras, a definite generic and specific 11 Description. MB.C.10080 (Pl. 13, fig. 11) is fragment of apical assignation will be possible only when more complete 6 mm. Conch straight with circular cross-section and smooth 12 conch fragments are found. surface. Tip blunt, after first 0.1 mm widening with angle of 13 expansion of 4 degrees up to 1.9 mm from tip, reaching cross- 14 section diameter of 1 mm. After 1.9 mm conch width slowly 15 decreases for next 2 mm towards cross-section diameter of Genus MEROCYCLOCERAS Ristedt, 1968 16 0.9 mm when it again increases at a very low angle of expansion. 17 Initial septa are 0.5, 0.5, 0.4, 0.5, 0.4, 0.5, 0.5 and 0.6 mm long Type species. M. declivis Ristedt, 1968, from the Kok Limestone, 18 from apex to adoral end of fragment. Maximum conch width of early Ludlow, of the Plo¨cken area, Carnic Alps, Austria. 19 apex occurs at fifth chamber. Fifth to seventh septa oblique, 20 forming conspicuous saddle on pro- or antisiphuncular side. Diagnosis (after Ristedt 1968). Slender, straight Orthocer- 21 Siphuncle eccentric. atidae with slightly compressed cross-section; angle of 22 Apical fragments MB.C.10079 (Pl. 13, fig. 12) and 10081 are expansion c. 3–5 degrees; with acute, obliquely transverse similar in general shape with a straight, blunt apical angle of 23 undulations, sloping adapically, forming wide lobe on expansion of 4 degrees after initial 0.1 mm, decreasing conch prosiphuncular side; undulation more pronounced in 24 width between 2 and 4 mm from tip, and subsequent increase early growth stages; sutures straight; septal distance about 25 with very low expansion rate. Initial septa of MB.C.10081 are 26 0.5, 0.25, 0.25, 0.4, 0.3, 0.4 and 0.5 mm long. Conch width in all one-third of cross-section; septal necks orthochoanitic; 27 fragments 1 mm at 5 mm from tip. septal perforation subcentral to eccentric; siphuncular seg- 28 ments tubular; diameter of siphuncular tube about one- 29 Remarks. The apices are questionably assigned to Kopan- seventh of conch cross-section; no endosiphuncular or 30 inoceras because they display medium septal spacing, a cameral deposits; apex with swollen first chambers. 31 32 33 34 EXPLANATION OF PLATE 9 35 Median sections of Orthocerida and Pseudorthocerida from the Filon Douze section. 36 Figs 1–2. Spyroceras latepatronus sp. nov., bed KMO-I, Pragian. 1, MB.C.9779 section shows short suborthochoanitic septal necks and 37 position and size of siphuncle. 2, MB.C.9694; detail of septal perforation and siphuncular segments. 38 Fig. 3. Spyroceras patronus (Barrande, 1866), MB.C.9778; bed KMO-II, Pragian; section shows short suborthochoanitic septal necks and 39 position and size of siphuncle. 40 Fig. 4. Spyroceras fukuijense? Niko, 1996, MB.C.9777; bed KMO-III, Pragian; note the short suborthochoanitic septal necks. 41 Fig. 5. Suloceras longipulchrum sp. nov., MB.C.9783, holotype; bed KMO-III, Pragian; detail of septal perforation and siphuncular 42 segment. 43 Fig. 6. Infundibuloceras mohamadi sp. nov., MB.C.9687, holotype; Erbenoceras Limestone, Zlı´chovian, Emsian; natural median section 44 showing shape and position of septal perforation. 45 Fig. 7. Kopaninoceras? jucundum (Barrande, 1870), MB.C.10085; bed OJ-I, Lochkovian; detail of septal perforation and conspicuous 46 shape of septal necks. 47 Fig. 8. Orthorizoceras desertum gen. et sp. nov., MB.C.9633; bed OSP-II, Prˇı´dolı´; detail of ventral side of siphuncular segments showing 48 two cyrtochoanitic septal necks and expanded connecting ring. 49 Fig. 9. Kopaninoceras thyrsus (Barrande, 1870), MB.C.10180; bed OP-M, Ludfordian, Ludlow; detail of septal perforation and 50 siphuncular segment. 51 Fig. 10. Kopaninoceras? dorsatoides sp. nov., MB.C.9700, holotype; bed OP-M, Ludfordian, Ludlow; section shows conspicuous 52 orthochoanitic septal necks and subcentral tubular siphuncular segments. Scale bar represents 10 mm. 53 Fig. 11. Infundibuloceras brevimira gen. et sp. nov., MB.C.9791; bed KMO-IV, Zlı´chovian, Emsian. Scale bar represents 10 mm. 54 Scale bars represent 1 mm except where indicated. PLATE 9 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 2 3 17 1 18 19 20 21 22 23 24 25 26 27 28 29 30 6 31 32 33 34 35 4 5 36 37 38 39 40 41 42 43 7 44 45 46 47 48 49 50 51 52 53 54 8 9 10 mm 1010 mm 11 KRO¨ GER, Orthocerida, Pseudorthocerida 64 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Remarks. Ristedt (1968, p. 247) provided only a very Description. MB.C.9787 is fragment of apical 3 mm with maxi- 2 short, imprecise original diagnosis. Here I add essential mum diameter of 1.3 mm at adoral end, ornamented with obli- 3 information, such as the form of undulations, shape of que, acute undulation that departs at an angle of 15–20 degrees 4 septal necks and position of the septal perforation, based from direction of growth throughout entire fragment. Distances 5 on the description of the type species provided by between annuli c. 0.1 mm. Apically, distances slightly greater than at adoral end of specimen where conch cross-section is cir- 6 Ristedt. cular or slightly compressed. Apical end of initial chamber blunt 7 Fragments of Merocycloceras that lack the apical part and undulation appears less conspicuous. Tip slightly bent. Ini- 8 cannot be distinguished from Plagiostomoceras; both have tial chamber slightly depressed, 0.5 mm long, with angle of 9 a strongly oblique ornamentation and aperture, a subcen- expansion lower than in subsequent growth stages. Maximum 10 tral tubular siphuncle, orthochoanitic septal necks, and a diameter of fragment is at 1.3 mm from tip where width is 11 slender shell with slightly compressed cross-section. 0.7 mm. 12 Therefore, it is possible that several species currently The three additional fragments known from bed KMO-I dis- 13 assigned to Plagiostomoceras will prove to be attributable play apical and second chambers only. The length and maxi- 14 to Merocycloceras when the apical characters are known. mum width of initial chamber in these specimens is 0.7 mm. 15 16 Occurrence. Wenlock–Pragian; Carnic Alps (Austria), Morocco Remarks. The specimens described above differ from M. 17 and Sardinia. declivis in having a higher angle of expansion. 18 19 20 Merocycloceras sp. A Merocycloceras? sp. C 21 Plate 13, figure 2 Plate 13, figure 14 22 23 Material. 1 apical fragment, MB.C.10179, from bed OJ-I, Loch- Material. 1 specimen, MB.C.9794, from bed OJ-I, Lochkovian, 24 kovian, Filon Douze section. Filon Douze section. 25 Description. The specimen is a fragment of apical 1.7 mm with 26 Description. Fragment of apical 4 mm; maximum diameter 0.7 mm at adoral end; ornamented with oblique, acute undula- maximum diameter of 0.6 mm at adoral end. Cross-section 27 tion. Angle of undulation initially strongly oblique, sloping compressed with a width to height ratio of 0.94. Ornament con- 28 adapically on prosiphuncular side nearly parallel to angle of sists of oblique, acute undulation, which departs c. 15–20 29 expansion of initial chamber; towards adoral end decreases degrees from direction of growth throughout entire fragment. 30 towards angles, departing 20–30 degrees from growth direction. Annuli c. 0.15 mm apart. Apical end of initial chamber acute 31 Distance of annuli c. 0.1 mm. Apically, distance of annuli and undulation appears less conspicuous. Tip slightly bent with 32 slightly wider than at adoral end of specimen. Conch cross-sec- siphuncle subcentrally positioned at convex side of growth axis. 33 tion circular or slightly compressed at adoral end. Apical end of Tip cross-section grows at apical 0.8 mm towards 0.6 mm. Ad- 34 initial chamber strongly depressed, forms flat, roof-shaped tip. apical of this position cross-section remains constant. 35 Tip slightly bent. Initial chamber 0.5 mm long. Shallow, wide 36 constriction occurs at 1.8 mm from tip where cross-section Remarks. The fragmentary nature of the specimen allows 37 diameter is 0.6 mm. Maximum diameter of fragment 1.3 mm only a questionable assignation to Merocycloceras. The from tip where cross-section diameter is 0.7 mm. Septal dis- 38 only definite diagnostic character visible is the oblique, tances between first four chambers are 0.5, 0.2, 0.2 and 0.3 mm acute undulation. The conch diameter does not expand 39 measured from tip to adoral end. 40 adorally of 0.8 mm from tip, which is probably evidence of a slightly swollen apical interval, another diagnostic 41 Remarks. The variability of the shape of the apex and character of Merocycloceras. The specimen differs from M. 42 ornamentation pattern is relatively high in the specimens declivis in having an acute tip. 43 of Merocycloceras figured by Ristedt (1968, pl. 1, figs 8– 44 11). The apex of MB.C.10179 differs from the specimens 45 described by Ristedt in having a strongly oblique initial Genus MICHELINOCERAS Foerste, 1932 46 ornamentation and a flattened initial chamber. 47 48 Type species. Orthoceras michelini Barrande, 1866, from the Upper Silurian of Bohemia, Czech Republic. 49 Merocycloceras sp. B 50 Plate 13, figure 3 Diagnosis (after Ristedt 1968, p. 53, and Kiselev 1971, p. 51 42). Slender orthocones with circular cross-section; angle 52 Material. 4 apical fragments, MB.C.9787, 9795–97, from bed of expansion very low, subcylindrical; shell surface 53 KMO-I, Pragian, Filon Douze section. 54 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 65

1 smooth; sutures straight; septal distance 0.5–1 of conch MB.C.10078 0.35, 0.2 and 0.3 mm long. In both fragments 2 cross-section; siphuncle central with diameter of 0.1 of conch width 0.5 mm at 5 mm from tip. 3 conch cross-section; siphuncular segments tubular; septal 4 necks long, orthochoanitic, length c. 0.25 of chamber Remarks. The shape of the initial chamber and the 5 length, form slightly concave tube; apex displays sub- smooth shell surface of these fragments are diagnostic of 6 spherical initial chamber with shallow initial apical con- Michelinoceras. They resemble Michelinoceras sp. 3 of Ser- 7 striction; no conspicuous second constriction. pagli and Gnoli (1977) and M. currens (Barrande, 1970). 8 Both also show only a shallow first apical constriction 9 Remarks. Serpagli and Gnoli (1977, p.172) remarked that and a subspherical initial chamber. However, they differ 10 Sphaerorthoceras Ristedt, 1968, is not clearly distinct from in being larger than M. currens and smaller than Michelin- 11 Michelinoceras Foerste, 1932, and thus questioned the oceras sp. 3, and the conch section adoral of the first con- 12 value of the former. Ristedt (1968, pl.1, fig. 1) illustrated striction also has a greater expansion rate than that of the 13 an apex of Michelinoceras michelini (Barrande, 1866) that latter form. 14 does not shows any apical constrictions; he also (p. 245) 15 emended the generic diagnosis and defined Michelinoceras 16 on the basis of its long, slightly concave septal necks and Genus ORTHOCYCLOCERAS Barskov, 1972 17 an apex that lacks conspicuous constriction. However, 18 Kiselev (1971, pl. 1. fig. 3) illustrated apices of M. miche- Type species. Orthocycloceras alayense Barskov, 1972, from the 19 lini that possess a shallow initial apical constriction. Thus, Upper Silurian of Isfara, Kazakhstan. 20 the shape of the apex of M. michelini shows some varia- 21 tion and the initial constriction does not appear to be a Diagnosis (after Zhuravleva 1978, p. 70). Orthocones or 22 reliable character for generic determination. The main very slightly cyrtocones with circular cross-sections; shell 23 diagnostic characters of Michelinoceras are the septal neck ornamented with straight, transverse lirae and with 24 shape and the very slender conch. The apically very simi- straight or slightly oblique undulations or faint ribs; sep- 25 lar Sphaerorthoceras differs in having shorter orthochoan- tal spacing wide or medium; sutures straight; siphuncle 26 itic or suborthochoanitic septal necks. central to eccentric with cylindrical segments; septal necks 27 orthochoanitic; endosiphuncular or cameral deposits not 28 Occurrence. Late Silurian–Early Devonian?; world-wide. known. 29 30 Occurrence. Middle Silurian–Early Devonian; world-wide. 31 Michelinoceras sp. 32 Plate 13, figures 16–17 33 Orthocycloceras? fluminense (Meneghini, 1857) 34 Material. 2 apical fragments, MB.C.10077–78, from limestone Plate 4, figures 8–9 35 nodules in bed OP-M, Ludfordian, Filon Douze section. *1857 Orthoceras (Cameroceras) fluminense Meneghini, 36 Description. MB.C.10077 (Pl. 13, fig. 17) is apical 5 mm. p. 188, pl. C, fig. 3a–c. 37 1866 Orthoceras bohemicum Barrande, pl. 214, figs 11–13; 38 Conch slightly bent with circular cross-section and smooth surface. Spherical initial chamber 0.5 mm in diameter. Initial pl. 215, figs 8–11; pl. 288, figs 1–15; pl. 289, 39 apical constriction has conch width of 0.45 mm and is figs 7–8; pl. 310, figs 16–19. 40 0.45 mm from tip. Conch adoral of initial constriction expands 1977 Orthocycloceras? fluminense (Meneghini); Serpagli 41 at angle of 13 degrees up to a distance of 2 mm from tip, and Gnoli, p. 178, pl. 5, fig. 2a–b, text-fig 9.[with 42 reaching cross-section diameter of 0.75 mm. After 2 mm, synonymy]. 43 conch width slowly decreases for next 1 mm, then adorally 1979 Orthocycloceras? fluminense (Meneghini); Gnoli 44 expands at very low angle. Initial septa 0.45, 0.2, 0.15, 0.15, et al., p. 418, table 4. 45 0.15 and 0.2 mm high, measured from apex towards adoral 1984 ‘Orthoceras’ fluminense (Meneghini); Dzik, pp. 108, 46 end of fragment. 112, pl. 30: fig. 7, text-fig. 42.11. 1988 Orthocycloceras aff. fluminense (Meneghini); 47 Apical fragment MB.C.10078 (Pl. 13, fig. 16) is similar in gen- eral shape with 0.5-mm-wide spherical initial chamber and first Go´mez-Alba, p. 352, pl. 173, fig. 4. 48 1991 Orthocycloceras fluminense (Meneghini); Gnoli and 49 apical constriction at 0.35 mm. Width of initial constriction 0.45 mm. Conch expands adorally of initial constriction at angle Serpagli, pp. 190, 194, pl. 3, fig. 2. 50 of 19 degrees up to 1.3 mm from tip where shallow second con- 1993 Orthocycloceras fluminense (Meneghini); Chlupa´cˇ, 51 striction occurs. Apex has angle of expansion of 4 degrees after pl. 6, fig. 7. 52 initial 0.1 mm, decreasing conch width 2–4 mm from apex, then 1999 Orthocycloceras? fluminense (Meneghini); Histon and 53 increasing width at very low expansion rate. Initial septa of Gnoli, p. 389, fig. 4C. 54 66 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Material. 4 specimens, MB.C.9612–15, from bed OSP-II; 1 speci- this species are poorly known. Unfortunately, the speci- 2 men (MB.C.9685) from BS, Prˇı´dolı´, Filon Douze section. mens collected from Filon Douze provides no additional 3 information since all are heavily recrystallized. They are 4 Diagnosis (compiled from Serpagli and Gnoli, 1977). Or- questionably assigned to Orthocycloceras because the shape 5 thocones with undulating shell; angle of expansion c.6 of their septal necks is unknown. 6 degrees; undulations rounded, oblique, sloping in adapical 7 direction on prosiphuncular side; undulations more obli- Occurrence. Wenlock–Prˇı´dolı´; Czech Republic, France, Morocco, 8 que in later growth stages (departure from growth axis Sardinia and Spain. 9 100–108 degrees); approximately three undulations at dis- 10 tance similar to conch cross-section; undulations gradu- 11 ally decrease towards antisiphuncular side, more marked Orthocycloceras tafilaltense sp. nov. 12 at later growth stages; ornamented with irregularly spaced Plate 10, figures 5–6; Plate 12, figure 1 13 striae or shallow ridges parallel to undulations and with 14 fine growth lines; septa simple, concave with spacing c. 2005 Cycloceras sp.; Kro¨ger et al., p. 331, pl. 4, figs E–F; 15 0.3 of conch cross-section; diameter of septal perforation pl. 5, fig. B. 16 0.1 of conch cross-section; siphuncle subcentral; septal 2008 Orthocycloceras sp.; Klug et al., pp. 44–45, pl. 5, figs 24–25, 27–30. 17 necks orthochoanitic with length c. 0.25 diameter of 18 septal perforation. Derivation of name. From Tafilalt, with reference to the type 19 region in Morocco. 20 Description. Largest specimen, MB.C.9612, 33 mm long, circular cross-section 29–31 mm in diameter (angle of expansion 3.5 21 Holotype. MB.C.9655 (Pl. 10, fig. 6; Pl. 12, fig. 1). 22 degrees). Undulations at distance of 10 mm oblique, sloping towards smoother conch side with departure from growth direc- 23 tion of c. 105 degrees. Maximum depth of valleys between ridges Type locality and horizon. Filon Douze section, bed KMO-II, 24 0.8 mm. Depth gradually decreases from side where undulations Pragian. 25 form shallow saddle to opposite side where they nearly die out. 26 Additionally ornamented with 10–11 rounded lirae per cycle of Other material. 2 specimens, MB.C.9780, 10134, from the type 27 undulations (10–11 per mm) running parallel to undulations. locality and horizon; 11 specimens, MB.C.10117–10128, from 28 Apical angle of other specimens varies between 7 and 9 degrees. bed EF, Zlı´chovian, the type locality. 29 30 Remarks. Despite the large number of descriptions and Diagnosis. Undulating orthocones with slightly com- 31 illustrations in the literature, the internal characters of pressed cross-section; angle of expansion 3–5 degrees; 32 33 34 35 EXPLANATION OF PLATE 10 36 Fig. 1. Suloceras longipulchrum sp. nov., MB.C.9783, holotype; bed KMO-III, Pragian; lateral view. 37 Figs 2–3. Hemicosmorthoceras semimbricatum Gnoli, 1982. 2, MB.C.9532; bed PK, Lochkovian; lateral view. 3, MB.C.10089; bed CK, 38 Lochkovian; lateral view. 39 Fig. 4. Theoceras filondouzense gen. et sp. nov., MB.C.10095, holotype; bed F, P. patulus conodont Biozone, early Eifelian; lateral view. 40 Figs 5–6. Orthocycloceras tafilaltense sp. nov. 5, MB.C.10117; bed EF, Zlı´chovian, Emsian; lateral view. 6, MB.C.9655, holotype; bed 41 KMO-II, Pragian; lateral view. 42 Figs 7–8. Plagiostomoceras reticulatum sp. nov., MB.C.10116; bed OJ-I, Lochkovian. 7, lateral view. 8, adapical view. 43 Figs 9, 14, 18. Plagiostomoceras culter (Barrande, 1866). 9, MB.C.9947; bed OP-M, Ludfordian, Ludlow; detail of shell surface of body 44 chamber showing faint oblique growth lines, lateral view. Scale bar represents 10 mm. 14, MB.C.9953; bed PK, Lochkovian; 45 mould of body chamber, lateral view. 18. MB.C.9943; bed PK, Lochkovian; mould of body chamber and five chambers of 46 phragmocone; lateral view. 47 Fig. 10. Anaspyroceras sp., MB.C.9680; bed KMO-III, Pragian; lateral view. 48 Fig. 11. Plagiostomoceras pleurotomum (Barrande, 1866), MB.C.9653; bed OP-K, Ludfordian, Ludlow; lateral view. 49 Fig. 12. Plagiostomoceras lategruenwaldti sp. nov., MB.C.9954; bed OJ-I, Lochkovian; lateral view. 50 Figs 13, 17. Plagiostomoceras bifrons (Barrande, 1866); bed OJ-I, Lochkovian. 13, MB.C.9944; lateral view. 17, MB.C.10088; juvenile 51 specimen; lateral view. 52 Fig. 15. Angeisonoceras reteornatum gen. et sp. nov., MB.C.9946, holotype; bed KMO-II, Pragian; lateral view. 53 Fig. 16. Pseudospyroceras reticulum gen. et sp. nov., MB.C.9788, holotype; bed KMO-II, Pragian; lateral view. 54 All specimens from the Filon Douze section and ·2 except where indicated by the scale bar. PLATE 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 4 16 5 6 17 3 18 19 10 mm 20 2 21 1 22 23 24 25 7 26 27 28 8 29 9 30 11 12 31 10 32 33 34 35 36 37 38 39 40 13 14 41 42 43 44 45 46 47 48 49 50 51 52 53 15 16 17 18 54 KRO¨ GER, nautiloids 68 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Description. Holotype is fragment of phragmocone 30 mm long, 2 cross-section circular with diameter 10–12 mm (angle of expan- 3 sion 3 degrees). Slightly oblique, transverse undulations sloping 4 in adoral direction on prosiphuncular side, forming shallow lobe 5 on antisiphuncular side and shallow sinus on prosiphuncular side (Pl. 10, fig. 6). Distance between undulations c. 3 mm (four 6 undulations occur at distance similar to conch cross-section). 7 Additionally, narrow transverse lirae and valleys parallel to 8 undulations occur, nine within 2 mm, c. 15 at distance similar 9 to one cycle of undulations. A B 10 MB.C.10117 27 mm long, cross-section diameter 7.5–9.5 mm 11 (angle of expansion 4.2 degrees). One cycle of undulations 12 occurs at distance similar to chamber height. Fragment has eight 13 complete chambers with chamber height of c. 2.7–3.5 mm (0.3– 14 0.5 of conch cross-section). Siphuncle subcentral. Siphuncular 15 segments tubular (Pl. 12, fig. 1). Septal perforation at most ad- 16 apical septum 0.8 mm (c. 0.1 of conch cross-section). Septal necks orthochoanitic, 0.5 mm long at most adapical septum. 17 Smaller fragments more slender with greater septal distance 18 and more distance between undulations. MB.C10117 (Pl. 10, fig. 19 5), fragment of juvenile body chamber and septum at base of 20 chamber, length 10 mm, cross-section diameter 2.5–3.4 mm 21 (angle of expansion 5 degrees). Undulations oblique, sloping in 22 adoral direction on prosiphuncular side at distance of 1.4 mm. 23 CDAdditionally six lirae occur per 1 mm, running parallel to undu- 24 lations (c. 9 per cycle of undulations). 25 26 Remarks. Orthocycloceras tafilaltense differs from juvenile 27 parts of Orthoceras agassizi Barrande, 1866, in having a thin, 28 tubular, nearly central siphuncle that lacks endosiphuncular 29 deposits. Orthocycloceras allapsum Zhuravleva, 1978, differs 30 in having a higher angle of expansion, more closely spaced 31 transverse striations, and non-oblique undulation. 32 33 34 EFGenus PSEUDOSPYROCERAS gen. nov. 35 TEXT-FIG. 18. Schematic median sections of septal necks of 36 selected Orthoceratidae. A, Michelinoceras michelini, after Sweet Type species. Pseudospyroceras reticulum sp. nov., from the Pra- 37 (1964b). B, Kopaninoceras jucundum; MB.C.10085. C, gian of the Filon Douze section. 38 Infundibuloceras brevimira; MB.C.9791. D, Tibichoanoceras 39 tibichoanum gen. et sp. nov.; MB.C.9949. E, Theoceras Derivation of name. Greek, pseudes, false, referring to the orna- mentation of this genus, which is similar to that of Spyroceras. 40 filondouzense gen. et. sp. nov.; MB.C.10095. F, Bogoslovskya 41 perspicua, after Zhuravleva (1978, pl. 3, fig. 4a). Theoceras differs from Bogoslovskya in having a transversely ornamented shell. Other species included. None. 42 Not to scale. 43 Diagnosis. Slender orthoconic, undulating longicones; 44 conch cross-section nearly circular; ornamented with 45 narrowly spaced, raised longitudinal and transverse lirae; 46 undulations slightly oblique, sloping in adoral direction distance between longitudinal lirae slightly greater 47 on prosiphuncular side; ornamented with rounded ridges than between transverse lirae, forming a reticulate orna- 48 parallel to undulations, 9–15 ridges occur per cycle of ment; two undulations at distance similar to distance 49 undulation; one cycle of undulation between two septa; between two successive septa; septal spacing wide, 50 sutures nearly straight; septal distance 0.3–0.5 of conch approximately two septa at distance similar to conch 51 cross-section; siphuncle subcentral with tubular segments; diameter; septal necks orthochoanitic; siphuncle central to 52 diameter of septal perforation c. 0.1 of conch cross- subcentral; siphuncular diameter 0.1 of conch cross- 53 section; septal necks orthochoanitic, length more than section. 54 one-half of diameter of septal perforation. 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 69

1 Remarks. Although the ornamentation of Pseudospyroc- Derivation of name. In honour of Theo Engeser, Berlin, who has 2 eras is similar to that of Spyroceras, the septal necks devoted much of the last decade to compiling a taxonomic data- 3 are orthochoanitic and the siphuncle is narrow, as in base of fossil non-ammonoid cephalopods. 4 typical Orthocerida. Niko (1996, fig. 4.10) described 5 spyroceratids with suborthochoanitic to orthochoanitic Other species included. None. 6 septal necks in ephebic growth stages; these differ from 7 Pseudospyroceras in having wider and more expanded Diagnosis. Slender, straight conch with circular cross-sec- 8 siphuncular segments and septal necks that are slightly tion; surface ornamented with minute transverse striae, 9 bent outwards. However, P. reticulatum is based on a which form shallow lateral lobes; angle of expansion c. 8– 10 single, relatively large fragment; additional material may 11 degrees; sutures straight, transverse or slightly oblique 11 indicate that it is from an adult Spyroceras. Pseudospy- with antisiphuncular side sloping towards apex; septal 12 roceras is probably related to Orthocycloceras or Kionoc- distance 0.4 of conch cross-section diameter; siphuncle 13 eras Hyatt, 1884. eccentric; siphuncular segments tubular; siphuncular 14 diameter c. 0.05 of cross-section; septal necks orthochoan- 15 Occurrence. Pragian; Morocco. itic, form funnel with smallest diameter at adapical tip of 16 necks; no cameral or endosiphuncular deposits. 17 18 Pseudospyroceras reticulum sp. nov. Remarks. Theoceras is similar to Bogoslovskya Zhuravleva, 19 Plate 7, figure 12; Plate 10, figure 16; Plate 12, figure 2 1978, in having a slender conch and a very narrow, eccen- 20 tric siphuncle (compare Text-fig. 18E–F). However, Bogo- 21 Derivation of name. Latin, reticulum, net, referring to the orna- slovskya differs in having a smooth shell and wider septal 22 mentation of the species. spacing. 23 24 Holotype. MB.C.9788 (Pl. 7, fig. 12; Pl. 10, fig. 16; Pl. 12, fig. 2). Occurrence. Eifelian; Morocco. 25 26 Type locality and horizon. Filon Douze section, bed KMO-II, Pragian. 27 Theoceras filondouzense sp. nov. 28 Plate 10, figure 4; Plate 12, figure 3; Text-figure 18E Other material. Known only from the holotype. 29 Derivation of name. From Filon Douze, with reference to the 30 Diagnosis. As for genus. type locality. 31 32 Description. Holotype is fragment of phragmocone 17 mm long, Holotype. MB.C.10095 (Pl. 10, fig. 4; Pl. 12, fig. 3; Text- 33 cross-section circular with diameter 19–20 mm (angle of expan- fig. 18E). 34 sion 6 degrees). Ornamented with four straight, transverse undu- 35 lations 5 mm apart, longitudinal lirae 0.3 mm apart, transverse Type locality and horizon. Filon Douze section, bed F, P. patulus 36 lirae 0.1–0.2 mm apart. Some longitudinal lirae more distinct conodont Biozone, early Eifelian. 37 than others, generally more prominent than transverse ones. 38 Three septa of holotype 7.5 and 9 mm apart. Diameter of perfo- Other material. 2 specimens, MB.C.10096–97, from the type 39 ration of adoral septum 1.7 mm. Septal necks orthochoanitic locality and horizon. 40 (Pl. 12, fig. 2). 41 Diagnosis. As for genus. 42 Remarks. This species, known only from a single frag- 43 ment, displays all the diagnostic characters that are Description. Holotype 14 mm long, cross-section circular, 15– 44 needed to distinguish it; the combination of orthochoan- 17 mm in diameter (angle of expansion 8 degrees). Ornamented 45 itic septal necks, an undulating shell and a reticulate with fine transverse striae that form shallow lateral lobes; distance 46 ornamentation is unique. It is assigned to the Orthocerat- between two striae c. 0.1 mm. Fragment displays three chambers. Distance between two most adoral septa 5.2 mm, between most 47 idae on the basis of the first of these characters. adapical chambers 4.6 mm. Septa slightly oblique, sloping adap- 48 ically on antisiphuncular side. Septal perforation at most adoral 49 septum 6.7 mm from conch margin with diameter of c. 0.7 mm Genus THEOCERAS gen. nov. 50 (0.05 of cross-section). Septal necks orthochoanitic, form funnel 51 with smallest diameter at tips. Siphuncular segments tubular. Type species. Theoceras filondouzense sp. nov. from the Eifelian 52 MB.C.10096 has poorly preserved surface; length 26 mm; of the Filon Douze section. 53 cross-section circular, 17–22 mm in diameter (angle of expan- 54 70 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 sion 11 degrees), with four chambers. Distance between two transverse, lobate striae (see Yu¨ 1930; Lai 1986) and has 2 most adoral septa 6.3 mm, between most adapical chambers endosiphuncular and cameral deposits that are character- 3 5.7 mm. Septa directly transverse. Septal perforation at most istic for lituitids. 4 adoral septum 8.6 mm from conch margin with diameter of c. 5 1 mm (0.05 of cross-section). Septal necks orthochoanitic, form Occurrence. Ludfordian–Emsian; Morocco, Ukraine and Russia. funnels with smallest diameter at tips (Pl. 12, fig. 3). Siphuncu- 6 lar segments tubular. 7 8 Tibichoanoceras tibichoanum sp. nov. 9 Plate 12, figure 6; Text-figure 18D Genus TIBICHOANOCERAS gen. nov. 10 Derivation of name. As for genus. 11 Type species. Tibichoanoceras tibichoanum sp. nov., from the Pra- 12 gian of the Filon Douze section. 13 Holotype. MB.C.9949 (Pl. 12, fig. 6; Text-fig. 18D). 14 Derivation of name. Latin, tibia, flute, referring to the narrow Type locality and horizon. Filon Douze section, bed KMO-I, 15 septal perforation with very long septal necks of this genus. 16 Pragian. 17 Other species included. Michelinoceras abditum Kiselev, in Bala- Other material. Only known from the holotype. 18 shov and Kiselev 1968; Sinoceras riphaeum Zhuravleva, 1978 19 (both species combined with Tibichoanoceras below: see ‘List of Diagnosis. Slender, straight conch with nearly circular 20 new combinations’). cross-section; surface smooth; angle of expansion below 6 21 degrees; sutures straight, transverse; septal distance 0.8 of 22 Diagnosis. Slender, straight conch with nearly circular conch cross-section; siphuncle central; siphuncular seg- 23 cross-section; surface smooth; angle of expansion below ments tubular; siphuncular diameter c. 0.1 of conch 24 10 degrees; sutures straight, transverse; septal distance cross-section; septal necks long, orthochoanitic, form 25 wide, more than 0.5 of conch cross-section; siphuncle straight tube; transition from septal necks to septa a sharp 26 central–eccentric; siphuncular segments tubular; siphun- angle of c. 90 degrees; length of septal necks c. 0.2 of 27 cular diameter c. 0.1 of conch cross-section; septal necks septal distance, 1.5 of diameter of septal perforation; 28 long, orthochoanitic, form straight tube; transition from thickness of septal necks gradually decreases towards tip 29 septal necks to septa a sharp angle of c. 90 degrees; thick- of necks. 30 ness of septal necks gradually decreases towards tip of 31 necks; no cameral or endosiphuncular deposits. Description. Holotype with smooth surface, 70 mm long, cross- 32 Remarks. Tibichoanoceras differs from Michelinoceras section circular, diameter 40–47 mm (angle of expansion 6 33 degrees). Fragment displays two complete chambers. Distance Foerste, 1932, in having a wider siphuncle and in the 34 between two most adoral septa 37 mm, between most adapical 35 shape of the septal necks. The septal necks of Michelinoc- chambers 32 mm. Septal curvature with depth of 18 mm at most 36 eras form a narrow funnel that gradually opens towards adoral septum. Sutures straight, transverse. Septal perforation at 37 the adoral and adapical end of the septal perforation, most adoral septum 5 mm in cross-section. Septal necks long, 38 whereas those of Tibichoanoceras form a straight tube orthochoanitic and straight. Transition from septal necks to septa 39 with a sharp angle at the transition between septum and a sharp angle of c. 90 degrees. Length of septal necks 7.5 mm at 40 septal neck (compare Text-fig. 18A, D). This septal neck most adoral septum, c. 0.2 of septal spacing, 1.5 of diameter of 41 shape is similar to that of Sinoceras Shimizu and Obata, septal perforation. Siphuncle central. Siphuncular segments tubular. 42 1935b, which is, however, ornamented with conspicuous 43 44 45 46 EXPLANATION OF PLATE 11 47 Lituitida from the Filon Douze section. 48 Figs 1, 3–5. Arthrophyllum vermiculare (Termier and Termier, 1950). 1, MB.C.9693; bed KMO-I, Pragian; weathered surface of lamellar 49 cameral deposits; ·2. 3, MB.C. 9697; bed KMO-I, Pragian; median section of apical conch section showing epichoanitic deposits 50 and lamellar deposits that partially cover the connecting ring which is not preserved. 4–5, MB.C.9648; bed KMO-V, Dalejian, 51 Emsian; median section showing expansion of lamellar cameral deposits and epichoanitic deposits in apical part. 52 Fig. 2. Sphooceras truncatum (Barrande, 1860), MB.C.9702; bed OP-M, Ludfordian, Ludlow; median section showing detail of septal 53 perforation and siphuncular segments; note the epichoanitic deposits. 54 Scale bars represent 1 mm. PLATE 11 1 2 3 4 5 6 7 8 9 10 1 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 2 3 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 4 51 52 53 54 5 KRO¨ GER, Lituitida 72 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Remarks. This species differs from Michelinoceras abditum preserved, rendering generic and specific determination 2 Kiselev, in Balashov and Kiselev 1968 in having a nar- impossible. 3 rower siphuncule and longer septal necks, and from Sin- 4 oceras riphaeum Zhuravleva, 1978 in having wider septal 5 spacing and a central siphuncle. Family ARIONOCERATIDAE Dzik, 1984 6 7 Genus ARIONOCERAS Barskov, 1966 8 Orthoceratidae gen. et sp. indet. 9 Plate 16, figure 3 Type species. Orthoceras canonicum Meneghini, 1843, from the 10 Wenlock of Cea di San Antonio, Fluminimaggiore, Sardinia, 11 Material. 1 specimen, MB.C.9913, from KMO-V, Daleijan, Italy. 12 Emsian, Filon Douze section. 13 Diagnosis (after Serpagli and Gnoli 1977, p. 182). Conch 14 Description. Fragment is complete body chamber with four straight or weakly curved, narrowly conical, moderately 15 chambers of phragmocone; total length 39 mm; conch cross-sec- dilating; angle of expansion c. 6–10 degrees; cross-section 16 tion nearly circular with adapical diameter of 9 mm, adoral circular to compressed; shell surface smooth or with shal- diameter 11 mm. Length of body chamber c. 22 mm. Maximum 17 low transverse sculpture; siphuncle central; septal necks cross-section diameter of specimen 12 mm and positioned at 18 suborthochoanitic, very short, acuminate, their lengths mid-length of body chamber. Aperture slightly constricted. less than diameter of septal foramen; connecting ring 19 Conch slightly cyrtoconic with siphuncle eccentrically positioned cylindrical; protoconch large, pointed apically, ogival in 20 on convex side of curvature of growth axis. Septal distances 4.3, 21 5.0, 5.6 and 3.5 mm, respectively, measured from adapical end. shape and bent ventrally; long caecum crosses whole pro- 22 Septal concavity relatively shallow with a depth of curvature of toconch; cameral deposits in apical chambers of adult 23 2 mm at most apical septum. Width of septal perforation specimens. 24 0.7 mm at conch cross-section of 10 mm in diameter where 25 length of orthochoanitic septal neck c. 0.8 mm. Siphuncular Remarks. Orthoceras arion Barrande, 1866, was chosen by 26 segments tubular. No endosiphuncular or cameral deposits. Barskov (1966) as type species of the genus. However, the 27 name is a junior subjective synonym of Orthoceras affine 28 Remarks. The fragment belongs to a mature individual, as Meneghini, 1857, which is preoccupied by O. affine Port- 29 indicated by the shape of the body chamber, which is lock, 1843. The next available valid name for O. arion is 30 constricted at the aperture, and by the crowded adoral Orthoceras canonicum Meneghini, 1857 (Serpagli and 31 septa. The specimen represents a small orthocerid that is Gnoli 1977; Gnoli 1998). 32 comparable in general form with Michelinoceras? sulcife- Serpagli and Gnoli (1977) described the cross-section 33 rum Zhuravleva, 1978, and Mericoceras Zhuravleva, 1978. of Arionoceras as circular. However, some variation from 34 However, the surface characters of the fragment are not this occurs in the type species. Herein, I extend the diag- 35 36 37 38 EXPLANATION OF PLATE 12 39 Median sections of Orthocerida from the Filon Douze section. 40 Fig. 1. Orthocycloceras tafilaltense sp. nov., MB.C.9780; bed KMO-II, Pragian; note the tubular siphuncle and orthochoanitic septal 41 necks; scale bar represents 1 mm. 42 Fig. 2. Pseudospyroceras reticulum gen. et sp. nov., MB.C.9788, holotype; bed KMO-II, Pragian; section shows position and size of 43 septal perforation and short, orthochoanitic septal necks. 44 Fig. 3. Theoceras filondouzense gen. et sp. nov., MB.C.10095, holotype; bed KMO-III, Pragian; note the eccentric position of siphuncle 45 and short, orthochoanitic septal necks. 46 Fig. 4. Arionoceras canonicum (Meneghini, 1857), MB.C.9879; bed OP-M, Ludfordian, Ludlow; note the very short septal necks. 47 Fig. 5. Infundibuloceras longicameratum gen et. sp. nov., MB.C.9705, holotype; bed PI, O. costatus conodont Biozone, Eifelian; note the 48 extremely large septal distance. 49 Fig. 6. Tibichoanoceras tibichoanum gen. et sp. nov., MB.C.9949, holotype; bed OJ-I, Lochkovian; detail of septal perforation and 50 conspicuous shape of septal necks. 51 Fig. 7. Temperoceras? ludense (Sowerby, in Murchison 1839), MB.C.9799; bed OP-M, Ludfordian, Ludlow; section shows characteristic 52 annular deposits. 53 Fig. 8. Arionoceras capillosum (Barrande, 1867), MB.C.10205; bed BS, Lochkovian. 54 Scale bars represent 10 mm except where indicated. PLATE 12 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 2 3 18 1 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 4 39 40 41 42 43 44 5 45 46 47 48 49 50 51 6 52 53 7 8 54 KRO¨ GER, Orthocerida 74 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 nosis to include forms with subcircular and compressed n 2 cross-sections but consider this to be a refinement of the 30 ntotal=144 3 wording of the diagnosis rather than an emendation. 25 4 The description of Arionoceras lotskirkense Kro¨ger, 5 2004, extended the generic time range of the genus to the 20 6 Middle Ordovician. However, the septal necks of the 15

7 Middle Ordovician species are considerably longer than 10 8 those of their Silurian counterparts and apical parts of 9 the species are not known, making the generic assignment 5 10 questionable. Hence, the generic time-range is considered 0 11 here to be Silurian–Early Devonian. 2.3 4.6 5.7 8 10.2 12.4 13.5 14.6 angle of expansion in degrees 12 13 Occurrence. Mid Silurian–Lochkovian; Armorican Massif TEXT-FIG. 19. Frequency distribution of angle of expansion (France), Carnic Alps (Austria), Czech Republic, Morocco and 14 of 144 specimens of Arionoceras canonicum. A clear single Sardinia. 15 frequency peak occurs at c. 7 degrees. 16 17 18 Arionoceras canonicum (Meneghini, 1857) 45 19 Plate 12, figure 4; Plate 13, figures 23–29 n=144 20 21 1857 Orthoceras affine Meneghini, p. 217, pl. C, fig. 16. 22 *1857 Orthoceras canonicum Meneghini, p. 199, pl. C, fig. 7a¢–a. 23 1866 Orthoceras arion Barrande, p. 221, fig. 2. 5.7 24 1977 Arionoceras affine. (Meneghini); Serpagli and Gnoli, 25 p. 182, pl. 6, figs 2–7, text-fig. 10b [with synonymy]. 26 1979 Arionoceras arion (Meneghini); Babin, in Babin 27 et al., p. 73, pl. 8, figs 5–11. angle of expansion in degrees angle of expansion 28 1998 Arionoceras affine (Meneghini); Gnoli, p. 2. 29 1998 Arionoceras arion (Meneghini); Gnoli, p. 2. 0.06 30 1999 Arionoceras affine (Meneghini); Histon and Gnoli: 1 10 100 31 pp. 384, 388, tables 1–2. conch cross section diameter in mm 32 TEXT-FIG. 20. Angle of expansion and average cross-section 33 Material. 142 fragments, MB.C.9800.1–141 and 9879, and 46 diameter of 93 fragments of Arionoceras canonicum. Note the 34 apices, MB.C.10231–10235, 10139.1–41, from bed OP-M, Lud- inconspicuous tendency of a lower angle of expansion in the fordian, Ludlow, Filon Douze section. 35 specimens with a larger cross-section. Axes logarithmically 36 scaled. Diagnosis (after Serpagli and Gnoli 1977, p. 182). Ariono- 37 ceratids with subcircular cross-section; angle of expansion 38 at adapical part of conch 5–6 degrees, increasing adorally 39 n to 7–8 degrees; shell surface ornamented with fine, irregu- 40 7 ntotal=47 lar growth lines, three per 1 mm; suture straight, trans- 41 verse; chambers short c. 0.5 of cross-section diameter; 6 42 depth of septal curvature one-third of septal distance; 5 43 siphuncle subcentral with diameter c. 0.17 of conch cross- 44 4 section; septal necks very short, suborthochoanitic–loxo- 45 choanitic; connecting rings slightly expanded within 3 46 chambers; mural and episeptal deposits in apical part of 47 2 adult specimens; initial chamber large, pointed apically 48 and ventrally bent, with width to length ratio of c. 0.83; 1 49 long ceacum crosses whole protoconch. 50 1.2 1.4 1.6 1.8 2.0 2.2 51 height of initial chamber in mm Description. Conch has nearly circular cross-section. Average 52 angle of expansion of 143 specimens 8 degrees (standard devia- TEXT-FIG. 21. Frequency distribution of height of initial 53 tion 2.3 degrees; maximum 15 degrees, minimum 3 degrees; chamber of 47 specimens of Arionoceras canonicum. Note the 54 two frequency peaks (compare with Serpagli and Gnoli 1977). 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 75

1 Text-fig. 19). No change in angle of expansion during growth Centre of septal perforation at most adoral septum 14.4 mm 2 visible (Text-fig. 20), but because fragments smaller than 5 mm from conch margin. Septal necks very short, suborthochoanitic. 3 in cross-section are usually preserved only as disarticulated Length of septal neck of most adoral septum 0.3 mm. Siphuncu- 4 chambers, estimation of expansion rate of early juvenile stages is lar segments slightly expanded within chambers, elliptical in 5 difficult. Variability of septal spacing relatively low. Septal dis- median section, forming constriction at septal perforation. Maxi- tance 0.3–0.5 of conch cross-section diameter. Sutures straight, mum diameter of siphuncular segment at most adoral chamber 6 transverse. Septal necks short. 2.8 mm. Average angle of expansion of all 65 specimens 6.3 7 MB.C.9879 62 mm long, cross-section diameter c. 14– degrees (standard deviation 2.3 degrees, maximum 12 degrees, 8 24 mm, with 11 complete chambers. Distance between cham- minimum 1 degree. Width to height ratio of 14 representative 9 bers varies between 3.8 and 6.3 mm. Length of second cham- specimens averages 0.91, maximum 0.96, minimum 0.84. 10 ber from adoral end of fragment 6 mm, with cross-section 11 diameter 20.6–21.5 mm. Septal perforations of two septa of Remarks. These specimens are distinguished from the 12 this chamber 1.6 mm. Centre of septal perforation 10.3 and type of A. canonicum in having a clearly compressed 13 9.2 mm from conch margin, respectively. Septal necks very cross-section. However, clear discrimination of a species 14 short, c. 0.2 mm, loxochoanitic. Siphuncular segments 1.8 mm with a compressed cross-section and A. canonicum with a in diameter, essentially tubular, forming constriction at septal 15 subcircular cross-section is impossible because all stages 16 perforation. Forty-seven apices with elongate, ovate initial chamber with between circular and compressed forms exist at Filon 17 acute tip and shallow apical constriction. Initial chamber slightly Douze. 18 bent. Long tubular ceacum present within initial chamber. Two 19 size classes can be distinguished (Text-fig. 21). Small apices with 20 initial chamber length 1.3–1.5 mm (Pl. 13, figs 25–26, 28) and Arionoceras capillosum (Barrande, 1867) 21 large apices with initial chamber length 2.0–2.2 mm (Pl. 13, figs Plate 12, fig 8; Plate 16, figures 5–6 22 23–24, 27, 29). In large and small apices constriction occurs at 23 cross-section diameter of 1.0–1.1 mm. Conch adoral of initial *1868 Orthoceras capillosum Barrande, pl. 325, figs 19–33; 24 constriction grows at angle of expansion of 8–9 degrees. Several pl. 357, figs 4–7; pl. 394, figs 16–19. 25 apices preserved as sparitic moulds of former cameral and sip- 1881 Orthoceras capillosum Barrande; Maurer, p. 27, pl. 2, 26 huncular spaces (Pl. 13, figs 23–26). fig. 5. 27 1890 Orthoceras capillosum Barrande; Whidborne, pp. 28 Remarks. This species was described in great detail by 129, 131. 29 Serpagli and Gnoli (1977); the description of the speci- 1914 Orthoceras capillosum Barrande; Chapman, pp. 206, 216. 30 mens here contribute to knowledge of the intraspecific variation. Serpagli and Gnoli (1977) did not include the 1950 Orthoceras cf. capillosum Barrande; Termier and 31 Termier, p. 36, pl. 132: figs 24–25. 32 term ‘loxochoanitic’ in their specific diagnosis. However, they emphasized the very short septal necks and their 1972 Michelinoceras capillosum (Barrande); Barskov, p. 37, 33 pl. 1, figs 3–4; pl. 2, fig. 4. text-figure 10 indicates that the species has loxochoanitic 34 1975 Caliceras capillosum (Barrande); Kolebaba, p. 389, 35 septal necks. This is not considered to be an emendation pl. 1, figs 1–4; pl. 2, figs 1–5; pl. 3. figs 1–6; pl. 4, 36 of the diagnosis, rather a more precise statement of what figs 1–3; text-figs 1, 3–4. 37 Serpagli and Gnoli (1977) expressed. 1977 Caliceras capillosum (Barrande); Kolebaba, p. 127, 38 text-fig. 1.2. ˇ´ ´ 39 Occurrence. Ludlow–Prıdolı; Armorican Massif (France), Carnic 1984 ‘Caliceras capillosum’ (Barrande); Dzik, pp. 97, 108, Alps (Austria), Czech Republic, Morocco, Russia and Sardinia. 40 112, text-fig 14. 1985 Caliceras capillosum (Barrande); Kiselev, p. 84, pl. 1, 41 fig. 12. 42 Arionoceras aff. canonicum (Meneghini, 1857) 1991 Caliceras capillosum (Barrande); Kiselev, p. 26, 43 Plate 16, figures 4, 7 text-figs 2.3–2.4. 44 45 Material. 65 fragments, MB.C. 9751.1–63, 10229-10230, from Material. 23 fragments, MB.C.10205–28, and 2 apical fragments, 46 bed OP-M, Ludfordian, Filon Douze section. MB.C.9591–92, from bed BS, Lochkovian, Filon Douze section. 47 48 Description. MB.C.10229 34 mm long, conch cross-section ellip- Diagnosis (after Kolebaba 1975, p. 389). Arionoceratids 49 tically compressed with width to height ratio of c. 0.9; width 22– with angle of expansion of 6–7 degrees; shell surface 50 28 mm, height 25–30 mm (angle of expansion 8.4 degrees). ornamented with marked fine transverse striae which 51 Specimen has four complete chambers; chamber length 6–7 mm. form shallow sinus on prosiphuncular side; sutures 52 Sutures transverse with shallow lateral lobes. Septal curvature of straight, transverse; chambers c. 0.3–0.8 of conch cross- 53 most adoral septum 7 mm. Diameter of septal perforation at section diameter; depth of septal curvature one-quarter of 54 most adoral septum 2.4 mm, which is 0.8 of conch cross-section. 76 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 conch cross-section; siphuncle subcentral; diameter of chamber. Siphuncular position subcentral. Septal perforation c. 2 septal perforation c. 0.1 of conch cross-section; septal 0.02 mm wide at conch cross-section diameter of 4 mm. Conch 3 necks very short, suborthochoanitic; connecting ring adoral of constriction grows at angle of expansion of 12 degrees. 4 slightly expanded within chambers; mural and episeptal 5 deposits in apical part of adult specimens. Remarks. The apical fragments described above differ 6 from those of A. canonicum in having an initial chamber 7 Description. Conch ornamented with conspicuous, closely <1 mm in length. 8 spaced, transverse lirae (Pl. 16, figs 5–6) which form shallow 9 sinus on prosiphuncular side, approximately eight in 1 mm in 10 MB.C.10206. Conch cross-section compressed or circular. Of 12 Genus ADIAGOCERAS gen. nov. 11 measured specimens, two have circular cross-section. Minimum measured width to height ratio of conch 0.89, average 0.95. 12 Type species. Adiagoceras taouzense sp. nov., from the Lochko- Angle of expansion c. 7 degrees. No change of angle of expan- vian of the Filon Douze section. 13 sion during growth visible. Variability of septal spacing relatively 14 low. Septal distance is 0.3–0.4 of conch cross-section diameter. Derivation of name. A contraction of Arionoceras and Diagoceras. 15 Sutures straight, transverse. In MB.C.10205 chamber length of Adiagoceras is similar to the former with regard to the general 16 most adoral chamber is 6.8 mm with conch cross-section of conch shape and internally similar to the latter. 17 16.6 mm. Septal perforation 0.9 mm in diameter. Siphuncular 18 segments of entire fragment nearly tubular with cross-section Other species included. Orthoceras subnotatum Barrande, 1868 19 diameter of 1.2 mm. Septal necks very short, loxochoanitic or (species combined with Adiagoceras below: see ‘List of new com- 20 suborthochoanitic. Length of septal neck of most adoral septum binations’). 21 of fragment 0.2 mm. Siphuncular tube slightly constricted at septal perforation. No cameral or endosiphuncular deposits pres- 22 Diagnosis. Short orthocones with angle of expansion of ent. Fragments MB.C.9591–9592 are apices with elongate-ovate, 23 slightly bent initial chamber; length of chamber 1.6 and 1.5 mm, 4–10 degrees; cross-section circular or ovate-compressed; 24 and diameter 1.1 and 1.0 mm respectively. Tips of initial cham- adult cross-section diameter <15 mm; shell ornamented 25 bers acute. Constriction between initial chamber and subsequent with conspicuous, minute, growth lines that describe shal- 26 conch weakly developed. Conch segment 1.4 mm adoral of ini- low lateral lobes; septal distance short, c. 0.3 of conch 27 tial chamber has angle of expansion of 12 degrees in MB.C.9591. cross-section diameter; sutures oblique, sloping in an ad- 28 apical direction on prosiphuncular side with shallow 29 Remarks. Kolebaba (1975) failed to include information lateral lobe; septal necks suborthochoanitic; septal perfo- 30 on the shape of the cross-section in the species diagnosis rations with diameter <0.1 of conch cross-section; sip- 31 of A. capillosum. The specimens figured by Barrande huncle initially subcentral, central in later growth stages; 32 (1874) and Kolebaba (1975) from the type locality and no endosiphuncular and cameral deposits; initial chamber 33 horizon are circular in cross-section. The specimens ovate, sometimes with acute tip; apical first 2 mm slightly 34 described here vary in cross-section from circular to com- cyrtocone with siphuncle on concave side of curvature of 35 pressed and may represent a different species. Because the growth axis. 36 known apices from bed BS of the Filon Douze section are 37 very similar to that of A. capillosum illustrated by Koleb- Remarks. Adiagoceras is assigned to the Arionoceratidae 38 aba (1975), these fragments are referred to this species, because of its similarity to Arionoceras in general conch 39 which differs from A. canonicum mainly in having a shape, the septal necks and shape of the apex. It differs 40 transversely ornamented conch. in having a smaller initial chamber, oblique sutures and 41 suborthochoanitic septal necks. It resembles Clinoceras 42 Occurrence. Ludlow–Lower Devonian; Australia, Czech Republic, Mascke, 1876, in general conch shape, but differs in 43 Germany, Morocco and Tadzhikstan. having suborthochoanitic septal necks and a compressed 44 conch cross-section. The oblique septa and eccentric 45 siphuncle are typical of Plagiostomoceras Teichert and 46 Arionoceras sp. A. Glenister, 1952, which differs in having orthochoanitic 47 Plate 13, figure 30 septal necks and a spherical apex. The Middle Devo- 48 nian Diagoceras Flower, 1936, is very similar in internal 49 Material. 7 apical fragments, MB.C.10236–41, from bed OP-M, characters, and also displays oblique septa and subor- 50 Ludfordian, Filon Douze section. thocoanitic septal necks, but differs in having a large 51 slender conch. The close similarity of Adiagoceras to 52 Description. Apices with small, elongate-ovate initial chamber of Diagoceras sheds new light on the phylogenetic affinities length 0.8 mm, maximum width 0.7 mm. Apical constriction 53 of the latter. Flower (1936, 1939) assigned Diagoceras to very shallow. Caecum elongate, tubular, crosses entire initial 54 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 77

1 the Pseudorthoceratidae but remarked (1939, p. 92) chamber ovate, sometimes with acute tip; apical first 2 that the’slender siphuncular segments of Diagoceras led 2 mm slightly cyrtocone with siphuncle on concave side 3 to its inclusion in the Orthoceratidae’. He considered it of curvature of growth axis. 4 to be an early offshoot of Dolorthoceras, but it is more 5 likely that it is a late representative of the Arionocerati- Description. Conch nearly straight, most apical 2 mm slightly 6 dae. However, data on the apex are needed in order to cyrtocone. Most apical part of conch slender with expansion of 7 solve this problem. Orthoceras subnotatum Barrande, <5 degrees. At cross-section diameter of c. 2 mm expansion rate 8 1868 is assigned to Adiagoceras herein because of its increases, resulting in slightly concave conch margins in median 9 general similarity to Adiagoceras taouzense. Gnoli (1982, section with angle of expansion up to 9 degrees (Text-fig. 22). Holotype with maximum cross-section diameter 8.7 mm, mini- 10 pp. 92–93) described the septal necks of O. subnotatum mum 7.4 mm, has angle of expansion of 6 degrees. Approxi- 11 as cyrtochoanitic. However, following the definition of mately 10 mm adoral of base of mature body chamber (at cross- 12 Kro¨ger (2006, p. 141), cyrtochoanitic septal necks have section diameter of 10 mm in MB.C.10106) expansion rate 13 brims that are bent more than 180 degrees. The septal decreases (compare Text-fig. 23). Mature body chamber of 14 necks of O. subnotatum are clearly bent <180 degrees MB.C.10106 has angle of expansion of 7 degrees where conch 15 and are, therefore, suborthochoanitic. margin in longitudinal section appears slightly convex. Cross- 16 section slightly compressed or circular. Conch surface orna- 17 Occurrence. Lochkovian; Czech Republic, Morocco and Sardinia. mented by faint growth lines of varying relief (Pl. 14, figs 1, 3). 18 Distance between prominent growth lines in MB.C.10105 1 mm. 19 Growth lines describe shallow lateral lobe. Septal spacing in 20 Adiagoceras taouzense sp. nov. MB.C.10106 with cross-section diameter of 9 mm, 1.2 mm; in holotype with cross-section diameter of 7.4 mm, 1.2 mm. 21 Plate 13, figures 5–7; Plate 14, figures 1–3; Plate 15, Mature septal crowding occurs in MB.C.10106 at cross-section figures 1–3 22 diameter of 9.8 mm with septal distance of most adoral septa 23 0.8 mm, where septal perforation is central and 1 mm in diame- 24 Derivation of name. From Taouz, a military station to the east ter. Septal necks suborthochoanitic (Pl. 15, figs 1–3). In holotype 25 of the type locality. at cross-section diameter of 7.4 mm centre of septal perforation 26 is 3.2 mm from conch margin and 0.4 mm in diameter. Apical 27 Holotype. MB.C.10151 (Pl. 15, figs 1–2). diameter at first septum c. 0.4 mm; length of first chamber c. 28 0.5 mm. Shape of initial chamber variably ovate, sometimes with 29 Type locality and horizon. Filon Douze section, bed OJ-I, Loch- acute tip, sometimes rounded. Apical first 2 mm slightly cyrto- kovian. 30 cone with siphuncle on concave side of curvature of growth axis 31 (Pl. 13, figs 5–7). In MB.C.10155 second to fourth chambers clo- Other material. 161 fragments of juvenile and mature specimens, sely spaced, only 0.1 mm apart. Height of fifth chamber 32 MB.C.9958.1–114, 10128.1–21, 10105–6, 10152, and 15 apices, 0.17 mm; of sixth, 0.2 mm. Septal perforation at most apical 33 MB.C.10153–10168, from the type locality and horizon; 1 frag- chambers half-way between centre and margin of conch. Posi- 34 ment, MB.C.9590, from bed CK, Lochkovian, from the type tion of septal perforation shifts in later septa increasingly 35 locality. towards centre. Most apical septum of apex oblique with subor- 36 thochoanitic septal neck. 37 Diagnosis. Short orthocones with angle of expansion 38 between 4 and 10 degrees; in earliest growth stages, conch Remarks. Although the angle of expansion can vary con- 39 slender; juvenile growth stages have highest angle of siderably between specimens (Text-fig. 22), it is impossi- 40 expansion; mature growth stages with medium expansion ble to distinguish two or more species of Adiagoceras 41 rate of c. 7 degrees; adult cross-section diameter c. using this character. Adiagoceras taouzense is the pre- 42 13 mm; cross-section circular at mature body chamber, dominant cephalopod in bed OJ-I of the Filon Douze 43 slightly compressed in adolescent stages; ornamented with section, which is composed almost entirely of fragments 44 conspicuous, minute, growth lines that describe slight lat- of all sizes of this species. The apex of A. taouzense dif- 45 eral lobes; distance between prominent growth lines in fers from the apices described and illustrated by Serpagli 46 adult specimen c. 1 mm; septal distance 0.3 of conch and Gnoli (1977, text-fig. 5), which they assigned to 47 cross-section; sutures oblique, sloping in adapical direc- Protobactrites? sp., in having a larger apical expansion 48 tion on prosiphuncular side with shallow lateral lobe; rate and oblique septa. Moreover, these Silurian apices 49 septal necks suborthochoanitic; diameter of septal perfo- have a more pronounced, constricted, and more elongate 50 ration <0.1 of conch cross-section; siphuncle initially sub- initial chamber. The initial chambers of species of Ario- 51 central, central in later growth stages; no endosiphuncular noceras, except A. submoniliforme (Meneghini, 1857), 52 and cameral deposits; apical diameter at first septum c. have different dimensions and differ in shape, mainly in 53 0.4 mm, length of first chamber c. 0.5 mm; initial having an acute tip; they are also clearly constricted in 54 78 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 later growth stages. No clear constriction occurs in Adi- Parakionoceras originale (Barrande, 1868) 2 agoceras. Orthoceras subnotatum Barrande, 1868 differs Plate 14, figures 4–5 3 from A. taouzense in having longer septal necks and an 4 ovate-compressed cross-section. 1855 Orthoceras originale Barrande, p. 450 [nomen 5 nudum]. 6 * 1868 Orthoceras originale Barrande, pl. 267, figs 1–20. 1874 Orthoceras originale Barrande, pp. 206–209. 7 Genus PARAKIONOCERAS Foerste, 1928 1882 Orthoceras originale Barrande; Blake, p. 110, pl. 7, 8 figs 5, 5a, 10. Type species. Orthoceras originale Barrande, 1868, from the mid 9 1914 Orthoceras originale Barrande; Vidal, p. 9, pl. 3, Silurian of Bohemia, Czech Republic. 10 fig. 8. 11 1928 Parakionoceras originale (Barrande); Foerste, p. 314. 12 Diagnosis (after Sweet 1964b, p. K229). Slightly cyrto- 1972 Parakionoceras originale (Barrande); Barskov, p. 47, 13 conic conch which increases moderately; conch surface pl. 1, figs 9–10; pl. 2, fig. 14. 14 vertically incised at regular intervals by very narrow, 1977 Parakionoceras originale (Barrande); Kolebaba, 15 shallow grooves; cross-section circular; septa transverse p. 133, pl. 2, fig. 5, text-fig. 5. 16 and widely spaced; septal necks short and loxochoanitic; 1977 Parakionoceras originale (Barrande); Serpagli and 17 siphuncle thin and subcentrally positioned on convex side Gnoli, p. 180, pl. 7, fig. 5. 18 of curvature of conch growth axis; siphuncular segments 1978 Parakionoceras originale (Barrande); Zhuravleva, p. 67, pl. 1, figs 9–10. 19 slightly constricted at septal necks, otherwise essentially cylindrical; no siphuncular deposits; presence or absence non 1984 Parakionoceras originale (Barrande); Dzik, pp. 108, 20 122, pl. 29, figs 1–2; pl. 30, figs 3–4; text-fig. 42.17 of cameral deposits not known. 21 [fide Turek and Marek 1986]. 22 1986 Parakionoceras originale (Barrande); Turek and 23 Occurrence. Wenlock–Lochkovian; world-wide. Marek, p. 252. 24 25 26 27 28 EXPLANATION OF PLATE 13 29 Apices from the Filon Douze section. 30 Fig. 1. Sphaerorthoceras sp. B., MB.C.9511; bed BS, Lochkovian. 31 Fig. 2. Merocycloceras sp. A., MB.C.10179; bed OJ-I, Lochkovian. 32 Fig. 3. Merocycloceras sp. B., MB.C.9787; bed KMO-I, Pragian. 33 Fig. 4. Parasphaerorthoceras sp. H Ristedt, 1968; MB.C.9521; bed BS, Lochkovian. 34 Figs 5–7. Adiagoceras taouzense sp. nov.; bed OJ-I, Lochkovian. 5, MB.C.10136. 6, MB.C.10155. 7, MB.10153. 35 Fig. 8. Bactrites? sp., MB.C.9764; bed KMO-III, Pragian. 36 Figs 9–10. Devonobactrites obliquiseptatum (Sandberger and Sandberger, 1852); bed EF, Zlı´chovian, Emsian. 9, MB.C.9548. 10, 37 MB.C.9549. 38 Figs 11–12. Kopaninoceras? sp.; bed OP-M, Ludfordian, Ludlow. 11, MB.C.10080. 12, MB.C.10079. 39 Fig. 13, 15. Akrosphaerorthoceras sp.; bed BS, Lochkovian. 13, MB.C.9627. 15, MB.C.9596. 40 Fig. 14. Merocycloceras? sp. C.; MB.C.9794; bed BS, Lochkovian. 41 Figs 16–17. Michelinoceras sp.; bed OP-M, Ludfordian, Ludlow. 16, MB.C.10078. 17, MB.C.10077. 42 Figs 18–19. Hemicosmorthoceras aichae sp. nov.; MB.C.9586, holotype; bed OJ-I, Lochkovian. 18, lateral view. 19, view on convex side 43 of growth axis. 44 Fig. 20. Sphaerorthoceras sp. A., MB.C.9510; bed BS, Lochkovian. 45 Fig. 21. Parasphaerorthoceras sp. B Ristedt, 1968; MB.C.9524; bed BS, Lochkovian. 46 Fig. 22. Parasphaerorthoceras sp. G Ristedt, 1968; MB.C.9517; bed PK, Lochkovian. 47 Figs 23–29. Arionoceras canonicum (Meneghini, 1857); note the variability in length of apical chambers. 23–28, bed OP-M, Ludfordian, 48 Ludlow. 23–24, MB.C.10234; mould of apical chambers showing negative impression of empty spaces of siphuncle and chambers 49 without cameral deposits. 23, lateral view. 24, prosiphuncular view. 25–26, MB.C.10235; mould of apical chambers showing shape 50 of long ceacum. 25, lateral view. 26, prosiphuncular view. 27, MB.C. 10231; lateral view. 28, prosiphuncular view. 29, MB.C.9591, 51 bed BS, Lochkovian; lateral view. 52 Fig. 30. Arionoceras sp. A., MB.C.10240; bed OP-M, Ludfordian, Ludlow; mould of apical chambers showing shape of caecum, lateral 53 view. 54 All ·15. PLATE 13 1 2 3 4 5 1 6 7 8 9 10 4 11 3 12 2 13 14 15 13 16 17 18 19 5 6 789 10 20 21 11 12 22 14 23 24 25 26 27 20 28 29 30 31 21 32 33 34 35 36 37 38 22 18 19 39 40 15 16 17 41 42 43 44 45 46 47 48 49 50 51 52 53 54 23 24 25 26 27 28 29 30 KRO¨ GER, nautiloids 80 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 n 45 2 10 n =47 3 total n=47 4 8 5 6 6 5.7 7 8 4 9 2

10 angle of expansion in degrees 11 0 0.06 12 2.3 4.6 5.7 8 10.2 12.4 13.5 14.6 1 10 13 angle of expansion in degrees conch cross section diameter in mm 14 TEXT-FIG. 23. Angle of expansion and average cross-section 15 TEXT-FIG. 22. Frequency distribution of angle of expansion diameter of 47 fragments of Adiagoceras taouzense gen et sp. 16 of 47 specimens of Adiagoceras taouzense gen et sp. nov. Note the single frequency peak at about 12 degrees. nov. Note the tendency towards lower angles of expansion in 17 the specimens with a larger cross section. Axes scaled 18 logarithmically. 19 1988 Parakionoceras originale (Barrande); Go´mez-Alba: 20 p. 352, pl. 173, fig 5. 21 Material. 4 fragments, MB.C.9518-19, 9948, 10132, from bed 22 OSP-II, Prˇı´dolı´; 1 fragment, MB.C.9520, from bed BS; 1 frag- Diagnosis (after Flower 1946, p. 139; Sweet 1964b,p. 23 ment, MB.C.9957, from bed CK; 2 specimens, MB.C.9516–17, K230). Dawsonoceratidae with slender orthoconic 24 from bed OJ-I, Lochkovian, Filon Douze section. conchs; surface ornamented with conspicuous transverse 25 undulations, longitudinal lirae, and faint transverse lirae; 26 Diagnosis (after Barskov 1972, p. 47). Parakionoceras with cross-section circular; septa transverse and closely 27 angle of expansion between 10 and 14 degrees, sometimes spaced; septal necks suborthochoanitic; siphuncle sub- 28 greater; ornamented with c. 60 longitudinal lacunae central; siphuncular segments tubular or slightly 29 around circumference; three septa at distance similar to expanded at septal necks; siphuncular and endocameral 30 conch cross-section diameter; diameter of siphuncle <0.1 deposits not known. 31 of conch cross-section; siphuncular segments nearly 32 tubular, slightly constricted at septal perforation. Remarks. For discussion of the family assignment of Ana- 33 spyroceras within the Dawsonoceratidae, see Kro¨ger and 34 Description. Largest fragment has cross-section diameter of Isakar (2006, p. 153). 35 21 mm (MB.C.10132), representing nearly tubular part of body 36 chamber. Distance between individual lacunae c. 1.1 mm. In Occurrence. Middle Ordovician–Early Devonian; Czech Republic, 37 MB.C.9518, diameter cannot be determined; however, distance Morocco and North America. 38 between individual lacunae 1.4 mm, with reference to original 39 fragment diameter of c. 26 mm. Fragment of phragmocone 40 MB.C.9957 16 mm long, cross-section diameter 7–9 mm (angle Anaspyroceras sp. of expansion 11 degrees), with slightly compressed cross-section. 41 Plate 7, figure 11; Plate 10, figure 10; Plate 15, figure 9 Chamber distance 3.1 mm. Position of siphuncle subcentral with 42 diameter of 0.9 mm. 43 Material. 1 specimen, MB.C.9680, from bed KMO-III, Pragian, Filon Douze section. 44 Occurrence. Wenlock–Lochkovian; Czech Republic, Kazakhstan, 45 Morocco, Spain and UK. 46 Description. Fragment slightly cyrtoconic, 27 mm long, circular 47 cross-section with diameter 9–11 mm (angle of expansion 4 degrees). Conch ornamented with undulations at distance of 48 Family DAWSONOCERATIDAE Flower, 1962 4 mm, longitudinal lirae 2.5 mm apart (nine occur across cir- 49 cumference), and closely spaced transverse lirae. Sutures trans- 50 Genus ANASPYROCERAS Shimizu and Obata, 1935a verse. Distance between septa 3.5 mm. Septal concavity shallow. 51 Septal perforations subcentral, diameter 1.1 mm at adoral end of 52 Type species. Orthoceras anellus Conrad, 1843, from the Beloit fragment (0.1 of conch-cross-section diameter). Septal necks 53 Member, Black River Formation, Ordovician of Mineral Point, suborthocoanitic. Siphuncular tube sightly expanded within 54 Wisconsin, USA. chambers and constricted at septal foramen. 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 81

1 Remarks. This fragment is assigned to Anaspyroceras Diagnosis. Slowly widening orthocones or cyrtocones cir- 2 because it displays suborthochoanitic septal necks and a cular or subcircular in cross-section with straight trans- 3 siphuncle that is only slightly expanded within the cham- verse or slightly oblique sutures; surface ornamented with 4 bers. It differs from A. pseudocalamiteum (Barrande, narrow transverse ridges and valleys approximately the 5 1851) in having a larger angle of expansion, a slightly cyr- same width, in some cases with longitudinal striae; aper- 6 toconic conch, and a longitudinal ornamentation that ture transverse with shallow hyponomic sinus; siphuncle 7 consists only of equally raised lirae. central; septal necks suborthocoanitic; siphuncular seg- 8 ments expanding slightly within camerae; small, adorally 9 attenuated, annulosiphonate deposits in adapical siphun- 10 Indet. Dawsonoceratidae cular segments; episeptal and hyposeptal deposits present. 11 Plate 15, figure 4 12 Remarks. This genus comprises species that are similar to 13 Material. 1 specimen, MB.C.10083, from bed KMO-I, Pragian, Geisonoceras Hyatt, 1884, in general conch shape and 14 Filon Douze section. ornamentation. However, in that genus, the surface has 15 broadly transverse bands with fine growth lines; Angeiso- 16 Description. Fragment of slightly cyrtoconic phragmocone noceras differs in having closely spaced transverse ridges. 17 13 mm long; conch cross-section nearly circular with diameter Although the sculpture of Geisonoceras rivale Barrande, 18 5.9–11.6 mm (angle of expansion of 24 degrees); 12 chambers 1859, is very conspicious and the generic diagnosis of present. Septal spacing close; minimum 1.2 mm (at adapical end 19 Sweet (1964b) refers to this ornamentation, the genus is of fragment), maximum 1.8 mm (at cross-section diameter of 20 13 mm). Siphuncle subcentral on convex side of growth axis. widely used as receptacle for Geisonoceratidae with a gen- 21 Diameter of septal perforation 0.5 mm at cross-section diameter erally transverse ornamentation. Of the 50 or more spe- 22 of 10 mm where diameter of siphuncle is 1.1 mm. Septal necks cies assigned to Geisonoceras when it was erected, several 23 achoanitic. Siphuncular segments essentially tubular with narrow should probably be assigned to Angeisonoceras, but of 24 constrictions at septal perforation. At adoral and adapical sur- these, I list only those illustrated by Barrande (1860–70). 25 faces of septa, large area of adnation of wide siphuncle. No en- 26 dosiphuncular and cameral deposits. Occurrence. Early Devonian; Czech Republic, Morocco and Sardinia. 27 28 Remarks. The internal structures of this fragment are 29 very distinctive. The septal necks are achoanitic and the Angeisonoceras reteornatum sp. nov. 30 nearly tubular siphuncle is strongly constricted at the Plate 7, figure 15; Plate 10, figure 15; Plate 15, figure 7 31 septal necks forming large areas of adnation. The very 32 short septal necks and the tubular siphuncle are diag- Derivation of the name. Latin, rete, net, with reference to the 33 nostic of the Dawsonoceratidae. However, no generic or characteristic ornamentation of the species. 34 specific determination is possible on the basis of this 35 single apical fragment because it does not show any Holotype. MB.C.9946 (Pl. 10, fig. 15; Pl. 15, fig. 7). 36 surface characters. 37 Type locality and horizon. Filon Douze section, bed KMO-II, Pragian. 38 39 Family GEISONOCERATIDAE Zhuravleva, 1959 Other material. 4 specimens, MB.C.9582–83 and 10092–94, from 40 the type locality and horizon. 41 Genus ANGEISONOCERAS gen. nov. 42 Diagnosis. Orthocones with slightly compressed cross-sec- 43 Type species. Orthoceras davidsoni Barrande, 1870, from the Upper Silurian of Lochkov, Bohemia, Czech Republic. tion; angle of expansion 5–8 degrees; ornamented with fine, 44 closely spaced, transverse ridges; ridges faintly undulating, 45 crossed by irregularly spaced, longitudinal, smooth striae; 46 Derivation of name. Contraction of the Latin angustus, narrow, with reference to the closely spaced transverse sculpture, and sutures straight, transverse at distance of c. 0.3 of conch 47 Geisonoceras Hyatt, 1884, which this genus otherwise resembles. cross-section; septal perforations subcentral with diameter of 48 0.1 of conch cross-section; septal necks suborthochoanitic. 49 Other species included. Angeisonoceras reteornatum sp. nov.; Or- 50 thoceras consocium Barrande, 1870; O. festians Barrande, 1870; Description. Holotype is fragment of body chamber and three 51 O. imminutum Barrande, 1870; O. inchoatum Barrande, 1868; O. chambers of phragmocone, 34 mm long; cross-section slightly 52 libens Barrande, 1870; O. limatum Barrande, 1870; O. squamatu- compressed, 21–26 mm in diameter (angle of expansion 8 53 lum Barrande, 1868 (all Orthoceras species combined with Ange- degrees). Conch surface only partially preserved with transverse 54 isonoceras below: see ‘List of new combinations’). ridges. Seven irregularly elevated ridges occur at distance of 82 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 1 mm, some more elevated than others, faintly irregularly fes- Occurrence. Late Silurian–Early Devonian; world-wide. 2 tooned. Irregularly spaced, longitudinal, smooth striae cross 3 transverse ornamentation. Septa transverse. Height of three 4 chambers measured from adapical to adoral, 7.3, 7.7 and Temperoceras? ludense (Sowerby, in Murchison 1839) 5 7.5 mm. Septal perforation subcentral with diameter 2.5 mm at Plate 12, figure 7 adapical septum. Septal necks suborthochoanitic, 1.3 mm long. 6 MB.C.10092, fragment of phragmocone 26 mm long; adoral 1839 Orthoceras ludense Sowerby, p. 619, pl. 9, fig. 1a–b. 7 diameter 15.3–17.8 mm (angle of expansion 5 degrees), orna- 1867–70 Orthoceras temperans Barrande, pl. 230, figs 7–9; 8 mented with faintly festooned transverse ridges (Pl. 7, fig. 15), pl. 327, figs1–2; pl. 382; pl. 451, figs 1–3. 9 eight occurring at distance of 1 mm, and longitudinal irregularly 1868 Orthoceras omnium Barrande, pl. 215, figs 2–3. 10 spaced smooth striae, crossing transverse ornamentation, form- 1870 Orthoceras dahlii Barrande, pl. 440, figs 7–10. 11 ing faint rectangular pattern. Siphuncle subcentral. Diameter of 1874 Orthoceras temperans Barrande, p. 658. septal perforation at most adapical septum 1.9 mm. 12 1876 Orthoceras ludense Sowerby; Remele´, p. 425. 13 1882 Orthoceras ludense Sowerby; Blake, p. 156, pl. 10, 14 Remarks. This species differs from all other species of the figs 1, 3–5, 7. 15 genus in having transverse striations that are crossed by 1925 Orthoceras temperans Barrande; Heller, p. 243. 16 longitudinal smooth striae. 1962 Temperoceras temperans (Barrande); Balashov and 17 Zhuravleva, pl. 12, fig. 2. 18 1966 Temperoceras temperans (Barrande); Babin, p. 324, 19 Genus TEMPEROCERAS Barskov, 1960 pl. 13, fig. 5; pl. 14, fig. 1a-c. 20 1972 Temperoceras temperans (Barrande); Barskov, p. 49, 21 Type species. Orthoceras ludense Sowerby, 1839, from the Gors- pl. 1, figs 1–2. 1999 Temperoceras temperans (Barrande); Histon and 22 tian (early Ludlow) of Ludlow, Shropshire, England; by subse- quent designation of Holland (2000). Gnoli, pp. 384, 388, tables 1–2. 23 2000 Temperoceras ludense (Sowerby); Holland, p. 120, 24 pl. 1, figs 3–4, 6–7; text-fig. 1 [with synonymy]. 25 Diagnosis (after Zhuravleva 1978, p. 75). Smooth ortho- cones with circular cross-section; septal spacing moderate; 26 Material. 6 specimens, MB.C.9512, 9508, 9576.1–3, 9799, from sutures straight or very slightly lobate; siphuncle sub- 27 bed OP, Ludfordian; 6 specimens, MB.C.9571.1–2, 9577.1–4, 28 central and with segments slightly expanded within from bed OJ-I, Lochkovian, Filon Douze section. 29 chambers; during ontogeny siphuncle position shifts suc- 30 cessively from centre and relative siphuncular diameter Diagnosis. Conch straight, slender, with angle of expan- 31 decreases; septal necks suborthocoanitic–orthochoanitic; sion of c. 7 degrees; conch cross-section circular; conch 32 endosiphuncular deposits form annuli at septal necks; surface smooth or very shallowly transversely undulating 33 cameral deposits on prosiphincular side of conch. at body chamber of late growth stages; irregularly spaced 34 35 36 37 EXPLANATION OF PLATE 14 38 Figs 1–3. Adiagoceras taouzense sp. nov., bed OJ-I, Lochkovian. 1, 3, MB.C.10105. 1, entire specimen, lateral view. 3, detail of conch 39 surface showing conspicuous growth lines; scale bar represents 1 mm. 2, MB.C.10157; adapical view. 40 Figs 4–5. Parakionoceras originale (Barrande, 1868); MB.C.9957; bed CK, Lochkovian; details of the conch surface with characteristic 41 longitudinal striae; scale bar represents 1 mm. 42 Figs 6–9. Devonobactrites obliquiseptatum (Sandberger and Sandberger, 1852); bed EF, Zlı´chovian, Emsian. 6, MB.C9545; body 43 chamber with large, healed, shell breakage at peristome; ventral view. 7, MB.C9546; section of phragmocone showing the closely 44 spaced, oblique septation. 8–9, MB.C9547; body chamber. 8, lateral view. 9, adapical view. 45 Figs 10–11. Lobobactrites ellipticus (Frech, 1897); MB.C.9580; bed F, P. partitus conodont Biozone, early Eifelian; 10, lateral view; 11, 46 adoral view. 47 Fig. 12. Bactrites gracilis (Blumenbach, 1803), MB.C.9945; bed F, P. partitus conodont Biozone, early Eifelian; natural section of 48 ventral part of conch. 49 Fig. 13. Kionoceras? doricum (Barrande 1868); MB.C.10101; bed OP-M, Ludfordian, Ludlow; lateral view. 50 Fig. 14. Temperoceras aequinudum sp. nov; MB.C.9505, holotype; bed KMO-III, Pragian; median section. 51 Fig. 15. Devonobactrites sp.; MB.C.1095; bed EF, Zlı´chovian, Emsian; lateral view. 52 Fig. 16. Sichuanoceras zizense sp. nov.; MB.C.9509, holotype; bed OJ-I, Lochkovian; median section, note the conspicuous annular 53 endosiphuncular deposits. 54 All specimens from the Filon Douze section and ·2 except where indicated by scale bar. PLATE 14 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 3 4 5 18 19 20 21 1 22 2 23 24 25 26 8 27 6 7 28 29 9 30 31 32 33 34 13 35 36 10 37 12 38 39 40 41 42 11 43 44 45 46 47 48 49 50 51 52 14 15 53 16 54 KRO¨ GER, nautiloids 84 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 conspicuous growth lines; septal distance 0.2–0.4 of conch Temperoceras aequinudum sp. nov. 2 cross-section; sutures straight, transverse; depth of septal Plate 14, figure 14 3 curvature equals depth of chambers; septal perforation 4 central or subcentral with diameter 0.1–0.2 of conch 2008 Temperoceras sp.; Klug et al.; pp. 45–46, pl. 6, 5 cross-section; siphuncular segments slightly expanded figs 19–22. 6 within chambers; septal necks suborthochoanitic, length 7 about half diameter of septal perforation; endosiphuncu- Derivation of name. Latin, nudus, naked, and with reference to 8 lar annuli at septal perforation; episeptal, mural, and hyp- Orthoceras nudum Barrande, 1870, which is similar in septal spacing, septal neck shape, and position of siphuncle. 9 oseptal deposits. 10 Holotype. MB.C.9505 (Pl. 14, fig. 14). 11 Description. MB.C.9799 from bed OP is fragment of two cham- bers 30 mm in total length; conch cross-section circular, diame- 12 Type locality and horizon. Filon Douze section, bed KMO-III, ter 45–47 mm. Depth of septal curvature 14 mm. Septal 13 Pragian. 14 perforation close to conch centre. Centre of septal perforation of 15 adapical septum 22 mm from conch margin. Diameter of septal perforation 8 mm. Septal necks suborthochoanitic, 3 mm long. Other material. 2 specimens, MB.C.9575.1–2, from bed OJ-II; 16 Siphuncular segments slightly expanded, maximum diameter at 10 specimens, MB.C.9755, 9758.1–9, from bed KMO-I; 27 17 midlength of 10 mm. At septal perforation endosiphuncular specimens, MB.C.5759.1–27, from bed KMO-II; 8 specimens, 18 annuli present. MB.C.5763.1–8, from bed KMO-III; 38 specimens, 19 MB.C.9508, from bed OJ-I is fragment of two chambers MB.C.5767.1–38, from bed EF, Lochkovian–Pragian, Filon 20 31 mm in total length; conch cross-section circular, diameter Douze section. 21 47–49 mm. Depth of septal curvature 16 mm. Septal perforation 22 close to conch centre. Centre of septal perforation of adapical Diagnosis. Conch straight with comparatively high angle 23 septum 24 mm from conch margin. Diameter of septal perfora- of expansion of more than 5 degrees; conch cross-section 24 tion 9 mm. Septal necks suborthochoanitic, 1.9 mm long. Sip- circular; septal distance c. 0.3 of conch cross-section; 25 huncular segments slightly expanded, maximum diameter at sutures straight, transverse; depth of septal curvature 26 midlength of 9.4 mm. At septal perforation endosiphuncular c. 0.5–0.7 (or less) of depth of chambers; septal perfora- annuli present. 27 tion subcentral with diameter 0.10–0.15 of conch cross- MB.C.9512, from bed OJ-I is fragment of two chambers 28 section; siphuncular segments strongly expanded within 29 mm in total length; conch cross-section circular, diameter chambers; septal necks suborthochoanitic, less than half 29 36–38 mm. Depth of septal curvature 11 mm. Septal perforation diameter of septal perforation in length; endosiphuncular 30 close to conch centre. Centre of septal perforation of adapical 31 septum 17 mm from conch margin. Diameter of septal perfora- annuli at septal perforation. 32 tion 5.6 mm. Septal necks suborthochoanitic, 1.3 mm long. 33 Connecting ring not preserved. No cameral and endosiphuncular Description. MB.C.9506 is largest fragment of phragmocone with 34 deposits present. 11 complete chambers and parts of shell surface, which is faintly irregularly undulating, otherwise smooth. Conch margin slightly 35 Remarks. The specific diagnosis is based on Holland convex in longitudinal section; cross-section circular. Fragment 36 115 mm long, cross-section diameter 32–53 mm (angle of (2000, pp. 120–121) and the illustrations of Orthoceras 37 expansion 10 degrees). Septal distance at cross-section diameter 38 temperans in Barrande (1867–70). Barrande’s material of 33 mm is 10 mm (0.3 of conch cross-section) where depth of 39 shows septal perforation of comparatively varied diame- septal curvature is c. 7 mm. Septal perforation subcentral 40 ter, ranging between 0.13 and 0.19 mm, as opposed to 15 mm from conch margin. Diameter of septal perforation 41 0.13–0.14 mm in Holland’s specimens. Thus, there is the 3.3 mm at conch cross-section diameter of 30 mm. Siphuncular 42 possibility that at least some of the specimens figured by segments strongly expanded within chambers with siphuncular 43 Barrande may be a separate species and that O. temperans diameter at mid-length between septa c. 6.5 mm. Shallow epi- 44 may encompass specimens with a wider siphuncle. How- septal and mural deposits occur on prosiphuncular side. 45 ever, more data are needed to confirm this conclusion. I Second largest specimen, MB.C.9956, is fragment of phragmocone with four complete chambers; total length 46 follow Holland (2000) herein and regard O. temperans and O. ludense as synonyms. Temperoceras ludense differs 64 mm. Conch margin slightly convex in longitudinal section; 47 cross-section circular, 43–49 mm in diameter (angle of expan- from all other species of the genus in having a compara- 48 sion 5 degrees), chamber distance varies between 0.3 (most 49 tively central siphuncle combined with moderate septal adoral chamber) and 0.23 (most adapical chamber) of conch 50 spacing and a deep septal curvature. cross-section. Depth of septal curvature 0.75–0.8 of chamber 51 distance. Septal perforation subcentral with centre of perfora- 52 Occurrence. Wenlock (Homerian)–Lochkovian; Czech Republic, tion of most adoral septum 23 mm from conch margin. Diam- 53 England, France, erratics in northern Germany, Kazakhstan, eter of septal perforation of most adoral septum 5.8 mm (0.12 54 Morocco and Sardinia. 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 85

1 of conch cross-section). Septal necks suborthochoanitic, 1 mm margin where diameter of septal perforation is 2.5 mm (0.14 of 2 long at most adoral septum. conch cross-section). Septal necks suborthochoanitic, 0.7 mm 3 MB.C.9505 is fragment of phragmocone with seven complete long. Siphuncular segments are nearly tubular. Thin hyposeptal 4 chambers; total length 56 mm; cross-section diameter 25–32 mm deposits present on prosiphuncular side. 5 (angle of expansion 7 degrees). Septal perforation subcentral with MB.C.10099 (Pl. 15, fig. 6) displays three complete chambers; diameter of 4.3 mm at most adoral septum (0.13 of conch cross- total length 23 mm; conch cross-section circular, diameter 14.9– 6 section). Endosiphuncular annuli present at septal perforation. 15.1 mm. Depth of curvature of most apical septum 3.6 mm. Sep- 7 tal perforation subcentral. Centre of septal perforation of most 8 Remarks. Temperoceras aequinudum is distinguished from apical septum 6.8 mm from conch margin where diameter of sep- 9 other species of the genus in having a combination of tal perforation is 1.7 mm (0.12 of conch cross-section). Septal 10 comparatively narrow septal spacing and a nearly central necks suborthochoanitic, 0.4 mm long. Siphuncular segments are 11 siphuncle that is strongly expanded within chambers. T. nearly tubular. Thin endosiphuncular annuli at septal perforation. 12 Specimens MB.C.9769.1–3 differ from Pragian specimens in nudum Barrande (1870) differs in having a wider siphun- 13 having a slightly wider siphuncle, c. 0.16 of conch-cross-section, cular diameter of 0.2 of conch cross-section and a lower 14 and a slightly closer septal spacing (distance between septa 0.4 of angle of expansion of 5 degrees. 15 conch cross-section). 16 17 Remarks. The diagnosis above is based on the illustrations Temperoceras migrans (Barrande, 1868) 18 of Barrande (1867–70). Temperoceras migrans is distin- Plate 15, figures 6, 8 19 guished from other species of the genus in its combina- tion of wide septal spacing, narrow, nearly tubular 20 non 1868 Orthoceras migrans Barrande, pl. 212, figs 1–4. 21 siphuncle and low angle of expansion. The four Emsian * 1868 –70 Orthoceras migrans Barrande, pl. 222, figs 1–2; specimens have a slightly wider siphuncle and slightly clo- 22 pl. 309, figs 1–4; pl. 348; pl. 377. ser septal spacing than the Pragian specimens. However, 23 1874 Orthoceras migrans Barrande, p. 643. 24 1878 Orthoceras cf. migrans Barrande; Kayser, p. 71, given the variation of the Bohemian specimens illustrated 25 pl. 10, fig. 6. by Barrande, this variability is regarded as intraspecific. 26 1968 Michelinoceras migrans (Barrande); Balashov and 27 Kiselev, p. 8, pl. 1, fig. 1. Occurrence. Ludlow–Lochkovian; Carnic Alps, Austria, Czech Republic, Harz Mountains (Germany), Kazakhstan, Morocco, 28 1972 Temperoceras migrans (Barrande); Barskov, p. 49, Sardinia and Ukraine. 29 pl. 4, fig. 1. 1998 Orthoceras migrans (Barrande); Histon, p. 108. 30 31 Material. 24 specimens, MB.C.9759.1–22, 9775, 10099, from bed Family KIONOCERATIDAE Hyatt, 1900 32 KMO-I; 2 specimens, MB.C.5760–61, from bed KMO-II; 3 speci- 33 mens, MB.C.9507, 9950–52, from bed KMO-III; 1 specimen, Genus KIONOCERAS Hyatt, 1884 34 MB.C.9592, from bed KMO-I; 3 specimens, MB.C.9769.1–3, 35 from bed KMO-V; Pragian–Dalejian, Filon Douze section. Type species. Orthoceras doricum Barrande, 1868, from the Upper 36 Silurian of Bohemia, Czech Republic. 37 Diagnosis. Conch straight, slender, angle of expansion 2– 38 3 degrees; cross-section circular; surface smooth; septal Diagnosis (after Sweet 1964b, p. K229). Conch slender to 39 distance 0.5–1 of conch-cross-section; sutures straight, rapidly expanding, apically curved and longitudinally flu- 40 transverse; depth of septal curvature c. 0.5–0.7 of depth of ted with circular to subcircular cross-section; ornament 41 chambers; septal perforation subcentral or slightly eccen- consists of prominent longitudinal ribs separated by con- 42 tric with diameter 0.10–0.16 of conch cross-section; sip- cave interspaces and, in most species, less conspicuous 43 huncular segments nearly tubular, very slightly expanded longitudinal and transverse lirae and striae; early formed 44 within chambers; septal necks suborthochoanitic, less than part of test may be faintly undulating; siphuncle central 45 half of diameter of septal perforation in length; endosip- to subcentral; septal necks short, suborthochoanitic; sip- 46 huncular annuli at septal perforation. huncular segments tubular, weakly expanded within 47 chambers; no endosiphuncular or cameral deposits. 48 Description. MB.C.9950 has smooth shell, circular cross-section 49 and very low angle of expansion; fragment 41 mm long, cross- Occurrence. The time range and geographic distribution of the 50 section diameter 17.5–19.5 mm (angle of expansion 2.8 degrees); genus is difficult to assess at present because it serves as a 51 five complete chambers (septal distance c. 0.5 of conch cross-sec- ‘wastebasket’ taxon for longitudinally ornamented orthocones 52 tion). Sutures straight, transverse. Depth of curvature of most with a variety of internal characters. It seems to be restricted to 53 apical septum 5 mm. Septal perforation subcentral. Centre of the Silurian. septal perforation of most apical septum 8.6 mm from conch 54 86 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Kionoceras? doricum (Barrande, 1868) occur between two first order lirae. Conch straight, without 2 Plate 14, figure 13 undulation. 3 MB.C.10102 is 33 mm long; cross-section diameter 13–18 mm 4 * 1868 Orthoceras doricum Barrande; pl. 269, figs 1–32. (angle of expansion 9 degrees). About 16 first order raised lirae 5 1928 Orthoceras doricum Barrande; Foerste, p. 285. occur around circumference and about six second order lirae occur between two first order lirae. At adoral end of fragment, a 6 1964 Kionoceras doricum (Barrande); Sweet, K229, third order of longitudinal lirae occurs, which are very closely 7 fig. 159.1a–c. 1977 Kionoceras doricum (Barrande); Serpagli and Gnoli, spaced, c. 8 per 1 mm. 8 p. 80, pl. 7, fig. 6a–c. 9 1979 Kionoceras doricum (Barrande); Gnoli et al., p. 418, Remarks. The generic diagnosis is based on Barrande’s 10 table 4. illustrations. The specimens here are very similar to those 11 non 1984 Kionoceras doricum (Barrande); Dzik, pp. 121, 126, illustrated by Barrande (1868) because the longitudinal 12 pl. 36, figs 3, 5, text-figs. striation consists of first and second order striae. How- 13 48, 49.19 [fide Turek and Marek, 1986]. ever, the distance between the first order striae of the 14 1999 Kionoceras doricum Histon and Gnoli, pp. 384, 388, Filon Douze specimens is greater than that of Barrande’s. tables 1–2. 15 A wide range of ornament occurs in the type material but 16 it is unclear if this reflects an intraspecific variability. 17 Material. 4 specimens, MB.C.100101–104, from nodules in bed OP-M, Ludfordian, Filon Douze section. Thus, a satisfactory species designation of the Filon Dou- 18 ze material will only be possible after revision of the type 19 material. 20 Diagnosis. Conch slightly curved in early growth stages, straight and slender in late growth stages; angle of expan- 21 Occurrence. Ludlow; Czech Republic, Sardinia and Morocco. 22 sion 5–9 degrees; adult size c. 30 mm in cross-section; 23 ornamented with raised longitudinal lirae and fine trans- verse striae; between first order longitudinal lirae up to 24 Family SICHUANOCERATIDAE Zhuravleva, 1978 25 five second order lirae, 20–25 first order lirae around cir- cumference; transverse striae very fine and festooned; in 26 Remarks. Zhuravleva (1978, p. 168) assigned the Sichua- early growth stages conch slightly undulating; septal dis- 27 noceratidae to the Bajkaloceratida. However, neither the tance c. 0.3 of conch-cross-section; sutures straight, trans- 28 Silurian–Devonian Sichuanoceratidae (nor the Offleiocer- verse; siphuncle central or subcentral with diameter 0.4 of 29 atidae) have anything in common with the Early conch cross-section; siphuncular segments tubular, 30 Ordovician Bajkaloceratidae except for the strong endo- slightly expanded within chambers; septal necks short, 31 siphuncular annuli that form rings with a subquadratic or suborthochoanitic. 32 rectangular shape in median section. In Baikaloceras Bala- 33 shov, 1962, the connecting rings are concave, the endosip- 34 Description. All four specimens only show surface characters. MB.C.10101 19 mm in diameter and has 15 first order lirae huncular deposits have longitudinal lamellae, and the 35 around circumference, which are distinctively raised above an chambers are short. These characters are typical of Early 36 otherwise nearly smooth surface. One or two second order lirae Ordovician ellesmerocerids, endocerids and intejocerids. 37 38 39 40 EXPLANATION OF PLATE 15 41 Median sections of Orthocerida and Pseudorthocerida from the Filon Douze section. 42 Figs 1–3. Adiagoceras taouzense sp. nov.; bed OJ-I, Lochkovian. 1–2, MB.C.10151, holotype. 1, section of three most adoral chambers 43 and base of body chamber. 2, detail of septal perforation and very short suborthochoanitic septal necks. 3, MB.C.10106; detail of 44 septal perforation and septal necks in chambers of juvenile specimen; note angular suborthochoanitic septal necks. 45 Fig. 4. Indet. Dawsonoceratidae; MB.C.10083; bed KMO-I, Pragian; note the short septal necks and the wide area of adnation. 46 Fig. 5. Kopaninoceras? jucundum (Barrande, 1870); MB.C.10085; bed OJ-I, Lochkovian; section shows shape of siphuncular segment 47 and septal neck. 48 Figs 6, 8. Temperoceras migrans (Barrande, 1868). 6, MB.C.10099; bed KMO-I, Pragian; details of shape of siphuncular segment and 49 septal necks. 8, MB.C. 9950; bed KMO-III, Pragian; section shows position and shape of siphuncle and suborthochoanitic septal 50 necks; scale bar represents 10 mm. 51 Fig. 7. Angeisonoceras reteornatum gen. et sp. nov.; MB.C.9946, holotype; bed KMO-II, Pragian; note the orthochoanitic septal necks; 52 scale bar represents 10 mm. 53 Fig. 9. Anaspyroceras sp.; MB.C.9680; bed KMO-III, Pragian; detail of siphuncular segment and septal necks. 54 Scale bars represent 1 mm except where indicated. PLATE 15 1 2 3 4 5 6 7 8 9 10 11 12 1 13 2 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 3 29 30 31 32 33 34 35 4 36 37 38 56 39 40 41 42 43 44 45 46 47 48 49 50 51 52 7 8 53 10 mm 10 mm 54 9 KRO¨ GER, Orthocerida, Pseudorthocerida 88 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 In contrast, the Sichuanoceratidae have relatively long Other material. 1 specimen, MB.C.9501, from the type locality 2 chambers, tubular or expanded siphuncular segments, and horizon. 3 and homogenous endosiphuncular annuli. Tsou (1966) 4 placed Sichuanoceras Chang, 1962, in the Pseudorthocer- Diagnosis. Sichuanoceras with slightly compressed 5 atidae. This cannot be accepted because the endosiphun- cross-section and angle of expansion of c. 5–6 degrees; 6 cular deposits in pseudorthoceratids are typically arranged surface smooth or with very fine, widely spaced, trans- 7 strongly asymmetrically in a longitudinal direction along verse growth lines; septal distance c. 0.4 of conch cross- 8 the septal perforation. In Sichuanoceras and its allies the section; depth of septal curvature nearly equals septal dis- 9 endosiphuncular deposits consist of annuli that are posi- tance; siphuncle eccentric with siphuncular segments 10 tioned nearly symmetrically around the septal perforation slightly expanded; segments with width to height ratio of 11 as in geisonoceratids. Therefore, the Sichuanoceratidae 0.8; diameter of septal perforation about one-fifth of 12 are considered to be a distinct group of the Orthocerida. conch cross-section; septal necks suborthochoanitic; 13 endosiphuncular deposits strongly asymmetrical in 14 dorsoventral direction, concentrated on ventral side of 15 Genus SICHUANOCERAS Chang, 1962 siphuncle. 16 17 Type species. Sichuanoceras quizhouense Chang, 1962, from the Description. Conch surface of holotype poorly preserved but 18 mid Silurian of Quizhou, China; by subsequent designation of apparently smooth or with only very fine, widely spaced, growth 19 Tsou (1966, p. 27). lines. Total length of holotype 30 mm; conch height 33–36 mm (angle of expansion 8.4 degrees), with two complete chambers; 20 adoral chamber 13 mm long; adapical chamber 15 mm long. 21 Emended diagnosis. Straight slender conch with circular or subcircular cross-section; surface marked with trans- Septal curvature of most adoral septum 11 mm. Septal perfora- 22 tion at most adoral septum 8.8 mm, which is 0.24 of conch- verse lines; sutures straight, transverse and with lobe on 23 cross-section. Centre of septal perforation 16.4 mm from conch 24 prosiphuncular side; siphuncle submarginal in position, margin. Septal necks suborthochoanitic, slightly bent. Length of 25 about one-third of conch cross-section in diameter; septal septal neck of most adoral septum 1.2 mm. Siphuncular seg- 26 necks suborthochoanitic; endosiphuncular deposits form ments slightly expanded within chambers, forming constriction 27 massive rings that can fill nearly entire siphuncular seg- at septal perforation. Maximum diameter of siphuncular seg- 28 ments; annuli positioned at septal perforation, nearly ment at most adoral chamber 10.3 mm. Endosiphuncular depos- 29 symmetrical in adoral and adapical directions, with sub- its consist of rings, positioned on ventral side of septal necks. 30 quadratical or rectangular shape in median section, typi- Ratio between length of adoral half and adapical half of rings is 1.1. Contact surface between two succeeding annuli perpendicu- 31 cally more developed on side of siphuncle that is closer to conch margin; hyposeptal and episeptal deposits. lar to length axis of siphuncle. Growth surfaces of annuli reveal 32 that they were initially elliptical or circular in longitudinal sec- 33 tion but in later growth stages rectangular with nearly straight Remarks. The diagnosis of Sichuanoceras largely follows 34 dorsal surfaces. At centre of each ring, at septal necks, narrow 35 Tsou (1966, p. 27) who, however, failed to provide infor- lamellae occur with a height of c. 0.3 of cross-section of septal 36 mation on the shape of the septal necks and details of the perforation. Dorsal one-quarter of siphuncle free of deposits in 37 endosiphuncular deposits, which are crucial for determi- holotype. 38 nation of the genus. Here, I include these characters, Second fragment 37 mm long; cross-section diameter 30– 39 which occur in the type species, based on his illustrations. 33 mm (angle of expansion 8.4 degrees); three complete 40 chambers with lengths between 13 mm (adoral chamber) 41 Occurrence. Mid Silurian–Early Devonian; China and Morocco. and 11 mm (adapical chamber). Septal curvature of most adoral septum 11 mm. Septal perforation at most adoral 42 septum 6.8 mm, which is 0.21 of conch cross-section. Centre 43 Sichuanoceras zizense sp. nov. of septal perforation c. 15 mm from conch margin. Septal 44 necks suborthochoanitic. Siphuncular segments slightly Plate 14, figure 16 45 expanded within chambers, forming constriction at septal per- 46 foration. Maximum diameter of siphuncular segment at most Derivation of name. From Qued Ziz, a large dry valley in south- 47 adoral chamber 8.8 mm. Endosiphuncular deposits as in holo- eastern Morocco, which crosses the Tafilalt in a north–south 48 type. direction to the east of Taouz. 49 Remarks. This species differs from all other species of 50 Holotype. MB.C.9509 (Pl. 14, fig. 16). 51 Sichuanoceras in having a relatively narrow siphuncle that 52 Type locality and horizon. Filon Douze section, bed OJ-I, Loch- is only weakly expanded within the chambers and also 53 kovian. positioned relatively close to the growth axis. 54 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 89

1 Family SPHAERORTHOCERATIDAE Ristedt, 1968 surface. Spherical initial chamber 0.25 mm in diameter. Initial 2 apical constriction has conch width of 0.25 mm at 0.2 mm from 3 Genus SPHAERORTHOCERAS Ristedt, 1968 tip. Initial constriction shallow. Conch adoral of initial constric- 4 tion expands with an apical angle of 12 degrees. Siphuncle central. 5 Type species. Sphaerorthoceras beatum Ristedt, 1968, from the 6 Gorstian (Ludlow) of the Massif de Mouthoumet, Aude, France. Remarks. The fragment differs from Sphaerorthoceras sp. 7 A in having a smaller initial chamber and a lower angle 8 Diagnosis (after Ristedt 1978, p. 53). Orthocones with cir- of expansion. 9 cular cross-section; shell surface smooth; sutures straight; 10 siphuncle subcentral; septal necks orthochoanitic or subor- 11 thochoanitic; apex with spherical initial chamber and deep Genus AKROSPHAERORTHOCERAS Ristedt, 1968 12 first constriction, without conspicuous second constriction. 13 Type species. Akrosphaerorthoceras gregalis Ristedt, 1968, from the Upper Silurian, cemetary in Fluminimaggiore, Sardinia, Italy. 14 Remarks. Serpagli and Gnoli (1977) remarked that Sph- 15 aerorthoceras is not sufficiently distinct from Michelinoc- Diagnosis (after Serpagli and Gnoli 1977, p. 175). Slender 16 eras Foerste, 1932, and thus questioned the value of the orthocones with circular cross-section; shell surface smooth 17 genus. However, M. michelini (Barrande, 1866), the type in early growth stages, transversely undulating in later 18 species, has elongate, slightly concave orthochoanitic sep- growth stages; sutures straight; siphuncle position eccentric; 19 tal necks and the apex shows only an inconspicuous first septal necks orthochoanitic; apex with conspicuous initial 20 and second apical constriction (see Ristedt 1968, p. 245). constriction and elongated initial chamber with acute, 21 Thus the diagnostic characters of Michelinoceras are very pointed tip; without conspicuous second constriction. 22 precisely known, even for the apical parts; its distinction 23 from Sphaerorthoceras is, therefore, justified. Occurrence. Wenlock–Lochkovian; Carnic Alps (Austria), Czech 24 Republic, Sardinia and Morocco. 25 Occurrence. Silurian–Late Devonian; Carnic Alps (Austria), 26 Czech Republic, Sardinia and Morocco. 27 Akrosphaerorthoceras sp. 28 Sphaerorthoceras sp. A. Plate 13, figures 13, 15 29 Plate 13, figure 20 30 Material. 1 apical fragment, MB.C.9593, from bed OSP-II, 31 ˇ´ ´ Material. 1 apical fragment, MB.C.9510, from bed BS, Lochko- Prıdolı; 3 apical fragments, MB.C.9596, 9627, 10084, from bed 32 vian, Filon Douze section. BS, Lochkovian, Filon Douze section. 33 34 Description. Apical fragment 0.9 mm long with adoral diameter Description. MB.C.9593 is fragment of apical 4 mm with adoral 35 of 0.6 mm. Conch slightly bent with circular cross-section and diameter of 0.5 mm. Conch slightly bent. Conch surface with 36 smooth surface. Spherical initial chamber 0.4 mm in diameter. shallow undulations of c. 0.25 mm. Elongate, acute initial cham- 37 Initial apical constriction has conch width of 0.5 mm at ber has maximum cross-section diameter of 0.2 mm. Shallow, 38 0.35 mm from tip. Conch adoral of initial constriction expands slightly oblique initial constriction occurs at 0.15 mm from tip. 39 with an apical angle of 22 degrees. Siphuncle central. Conch section adoral of initial constriction slightly inflated, 0.4 mm in maximum cross-section diameter 0.75 mm from tip. 40 Conch adoral of initial constriction until position of maximum Remarks. The spherical initial chamber and smooth shell 41 inflation expands with apical angle of 18 degrees. Adoral of 42 surface of these fragments are diagnostic of Sphaerorthoc- maximum inflation, conch nearly tubular. 43 eras, but fragmentary nature and poor preservation of the Three specimens from bed BS show very little morphological 44 material prevents specific determination. variation. MB.C.9627 (Pl. 13, fig. 13) is representative of all 45 three. It is a fragment of apical 1.5 mm with adoral diameter of 46 0.5 mm. Conch slightly bent; cross-section circular; siphuncle 47 Sphaerorthoceras sp. B. eccentric. Conch surface with shallow undulations of c. 48 Plate 13, figure 1 0.25 mm. Elongate, acute initial chamber has maximum cross- 49 section diameter of 0.25 mm. Shallow, slightly oblique initial 50 Material. 1 apical fragment, MB.C.9511, from bed BS, Lochko- constriction occurs 0.2 mm from tip. Conch section adoral of initial constriction slightly inflated, 0.5 mm in maximum cross- 51 vian, Filon Douze section. section diameter 1.25 mm from tip. Conch adoral of initial con- 52 Description. Apical fragment 0.9 mm long with adoral diameter of striction to maximum inflation expands with apical angle of 14 53 degrees. Adoral of maximum inflation, conch nearly tubular. 54 0.4 mm. Conch straight with circular cross-section and smooth 90 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Remarks. The acute, elongate initial chamber and slightly expansion of c. 27 degrees; initial constriction occurs at sec- 2 undulating shell surface of the fragments described above ond septum; second constriction leading to slender, slowly 3 are diagnostic of Akrosphaerorthoceras. However, no spe- widening conch with initial conch width of 0.9 mm and 4 cies has been described with undulation starting directly angle of expansion of 2–3 degrees; conch section apical of 5 at the tip. The fragmentary character and the poor preser- second constriction bent with turning point at second con- 6 vation of the specimens prevents specific determination. striction and at an angle of 20 degrees. 7 8 Description. Fragment 4.5 mm long, consisting of three sections: 9 Genus HEMICOSMORTHOCERAS Ristedt, 1968 initial shell, inflated conch section, and shaft. Initial shell subspher- 10 ical, 0.5 mm wide, separated from subsequent conch by conspicu- 11 Type species. Hemicosmorthoceras laterculum Ristedt, 1968, from ous constriction 0.3 mm from tip. Adoral of initial constriction 12 the basal limestone of the Rhynchotrypa megaera Beds, Ozarkodi- conch expands at an angle of 27 degrees towards width of 1.25 mm at 1.75 mm from tip, at which point cross-section depressed; width 13 na eosteinhornensis conodont Biozone, Ludfordian (Ludlow) of Cellon, Plo¨ckenpass, Carnian Alps, Austria. 1.5 mm; height 1.25 mm. At 1.75–2.25 mm from tip, conch width 14 and height decrease strongly and cross-section becomes circular or 15 Emended diagnosis. Slender, slightly compressed ortho- slightly compressed. Inflated part of fragment slightly ornamented 16 with transverse undulation. Distance between ridges of undulation cones ornamented with transverse striae, undulations or 17 c. 0.25 mm. Remaining part of conch smooth. Adoral of inflated 18 smooth; sutures straight; siphuncle subcentral; septal conch section, shaft follows; this is 2.5 mm long, and expands at 19 necks orthochoanitic; apex with conspicuous first and sec- angle of 2–3 degrees from 0.9 to 1 mm. Cross-section of shaft cir- 20 ond constriction, forming ovate or spherical initial cham- cular or slightly compressed. At second constriction conch bent, 21 ber and strongly inflated conch section between apical forming angle between initial shell and shaft of c. 20 degrees. Sec- 22 constrictions; apical conch shallowly undulating, with ond septum occurs at position of initial constriction, tenth septum 23 compressed cross-section; second constriction leading to at second constriction c. 2.1 mm from tip. 24 slender, slowly widening conch with initially, clearly smal- Remarks. The conspicuous initial constriction, the broadly 25 ler cross-section diameter than conch section adapical of inflated conch section adoral of the initial constriction, and 26 second constriction. the smooth, slender shaft are diagnostic of Hemicosmor- 27 thoceras. However, the conspicuous curvature between ini- 28 Remarks. Ristedt’s (1968, p. 279) diagnosis is very short tial shell and shaft and the ornamented inflated part of the 29 and provides only apical characters. Here, I include infor- apex are unique within the genus. The specimen described 30 mation on the shape of the septal necks and add some above is probably a complete juvenile conch with the last 31 details on the characteristic shape of the apical conch septum at the second constriction. However, it is possible 32 based on the original illustration and description of the that more adoral septa are not preserved. 33 type species. Hemicosmorthoceras differs from other sph- 34 aerorthoceratids in having a depressed, strongly inflated 35 apical conch section. Hemicosmorthoceras semimbricatum Gnoli, 1982 36 Plate 10, figures 2–3 37 Occurrence. Ludlow–Lochkovian; Bohemia, Carnic Alps (Aus- tria), Czech Republic, Morocco, Sardinia and Wales. 38 1982 Hemicosmorthoceras semimbricatum Gnoli, p. 75, 39 pl. 1, figs 1–3; text-fig. 2a–d. 40 Hemicosmorthoceras aichae sp. nov. 1994 Hemicosmorthoceras semimbricatum Gnoli; Evans, 41 Plate 13, figures 18–19 p. 127. 42 43 Derivation of name. In honour of Aicha, elder daughter of Filon Material. 1 specimen, MB.C.9530, from limestone nodules in bed 44 Douze miner Lahcan Caraoi. OP-M, Ludfordian, Ludlow; 2 specimens, MB.C.10135–36, from 45 bed OSP-II, Prˇı´dolı´; 2 specimens, MB.C.9532–33, from bed PK; 4 46 Holotype. MB.C.9586 (Pl. 13, figs 18–19). specimens, MB.C. 9529, 10089–91, from bed CK; 80 specimens, 47 MB.C.9534.1–80, from bed OJ-I, Lochkovian; Filon Douze section. 48 Type locality and horizon. Filon Douze section, bed OJ-I, Loch- 49 kovian. Emended diagnosis. Straight, slender orthocone with ellip- 50 tically compressed cross-section; angle of expansion of 51 Other material. Known only from the holotype. conch height <5 degrees; ornamented with shallowly 52 imbricated costae on prosiphuncular side; costae slope 53 Diagnosis. Hemicosmorthoceras with strongly inflated adorally and become indistinct on lateral and antisiphun- 54 conch section between apical constrictions with angle of cular sides, directly transverse on antisiphuncular side 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 91

1 and curved towards apex on lateral side; sutures straight similar pattern in a number of specimens collected in 2 and slightly oblique; septal distance approximately equals Sardinia. The specimen MB.C.9517, assigned here to 3 conch cross-section diameter; septal perforation slightly Parasphaerorthoceras sp. G. sensu Ristedt 1968, also dis- 4 eccentric, one-tenth of conch height in diameter; septal plays a loss of ornamentation with increasing size. 5 necks orthochoanitic, length similar to diameter of septal Hence, this character is considered diagnostic of the 6 perforation. Endosiphuncular and cameral deposits not genus. 7 known; embryonic conch smooth. 8 Occurrence. Wenlock–late Middle Devonian; Carnic Alps (Aus- 9 Description. Largest specimen (MB.C.9529) is a fragment of tria), Czech Republic, Sardinia and Morocco. 10 body chamber 26 mm long; conch at adapical end (= position 11 of last septum) 13 mm high and 11 mm wide; height at adoral 12 end 15 mm. Cross-section compressed, slightly ovate with sip- Parasphaerorthoceras sp. B sensu Ristedt 1968 13 huncle in narrower half of section. Depth of septal curvature Plate 13, figure 21 3.4 mm. Septal perforation 5 mm from conch margin. On pros- 14 iphuncular side conch ornamented with shallowly imbricated 15 1968 Parasphaerorthoceras sp. B; Ristedt, p. 269, pl. 4, ridges. Width of fine grooves between ridges c. 1.2 mm. Impres- fig. 3–3a; text-fig. 4.1c. 16 sion of the conch surface in MB.C.9532 reveals that costae 17 1977 Parasphaerorthoceras sp. B. Ristedt; Serpagli and curved towards apex on lateral side (Pl. 10, fig. 2). Gnoli, p. 169, pl. 4, fig. 9. 18 19 Remarks. Gnoli’s (1982, p. 76) diagnosis is modified above Material. 1 fragment, MB.C.9524, from bed BS, Lochkovian, 20 to include information on the adult; several references were Filon Douze section. 21 made to the alleged small size of the adult of this species 22 but no measurements were provided. Some of the Filon Description. Fragment of apical 1.5 mm of conch; adoral diame- 23 Douze specimens are clearly larger than that illustrated by ter 0.8 mm. Conch cross-section circular. Initial chamber elon- 24 Gnoli but are similar in all aspects of conch morphology. gate egg-shaped, 0.8 mm long, diameter at first septum 0.5 mm; 25 The species is easy to distinguish from other species of similar at initial constriction. Inflated section of conch adoral of 26 Hemicosmorthoceras by its oblique, imbricate costae that initial contriction only partly preserved but shows typical convex 27 cover exclusively the prosiphuncular side of the conch. conch margins in lateral view. Surface ornamented with straight, 28 directly transverse undulation; ten undulations occur within a distance of 1 mm. 29 Occurrence. Ludlow (Ludfordian)–Lochkovian; Morocco and 30 Sardinia. 31 Remarks. The egg-shaped initial chamber and low angle of 32 expansion adoral of initial constriction are diagnostic of Parasphaerorthoceras sp. B sensu Ristedt 1968. The fragment 33 Genus PARASPHAERORTHOCERAS Ristedt, 1968 34 described above shows these characters but is generally lar- ger and the initial constriction is more conspicuous than in 35 Type species. Parasphaerorthoceras accuratum Ristedt, 1968, from Ristedt’s specimen. A satisfactory species designation must 36 the Ozarkodina eosteinhornenis conodont Biozone, Ludfordian of 37 Plo¨ckenpass, Carnic Alps, Austria. wait until better material is available. 38 39 Diagnosis (after Ristedt 1968, p. 267). Orthocones with Occurrence. Wenlock–Lochkovian; Morocco and Sardinia. 40 circular cross-section; shell surface undulating apically 41 and smooth or striated in later growth stages; straight Parasphaerorthoceras sp. G sensu Ristedt 1968 42 sutures; central or subcentral siphuncle; septal necks sub- Plate 13, figure 22 43 orthochoanitic; apex with spherical initial chamber and 44 deep first constriction; without conspicuous second con- 1968 Parasphaerorthoceras sp. G; Ristedt, p. 274, pl. 4, 45 striction. fig 4; pl. 5, fig. 3. 46 47 Remarks. Ristedt’s (1968) diagnosis of Parasphaerorthoc- Material. 1 fragment, MB.C.9517, from nodule in bed PK, Loch- 48 eras is very short, indicating that it is a sphaerorticera- kovian, Filon Douze section. 49 tid with undulating apical growth stages. Additional 50 characters of the type species are included here. Special Description. An impression of apical 17 mm of conch; cross-sec- 51 emphasis is placed on the morphology of later growth tion 1.7 mm at adoral end. Initial chamber 0.8 mm long, and at 52 stages. The type specimen is undulating apically, later initial constriction 0.8 mm wide. Initial chamber subspherical 53 develops smooth striae, and then becomes smooth in and smooth. Subsequent conch section slightly inflated; maxi- 54 late growth stages. Serpagli and Gnoli (1977) found a mum width 1.2 mm at 2.0 mm from tip. Adoral of c. 3mm 92 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 from tip conch grows with angle of expansion of 5 degrees. Api- Occurrence. Wenlock–Lochkovian; Morocco and Sardinia. 2 cal part of impression ornamented with slightly oblique, acute 3 undulations; seven undulations occur within a distance of 4 1 mm. Distinctiveness of undulation decreases towards adoral Genus PLAGIOSTOMOCERAS Teichert and Glenister, 1952 5 end of specimen. Adoral of c. 7–8 mm from tip, shell surface smooth. 6 Type species. Orthoceras pleurotomum Barrande, 1866, from the 7 Colonograptus colonus Biozone, Kopanina Formation, Gorstian Occurrence. Wenlock–Lochkovian; Morocco. 8 (Ludlow) of Na Brekvici, Prague-Butovice, Bohemia, Czech 9 Republic. Remarks. Ristedt’s (1968) single specimen of P. sp. G, 10 collected from the Upper Silurian of the Moroccan Mese- Diagnosis (after Teichert and Glenister 1952, p. 741, and 11 ta, has a large initial chamber, relatively inconspicuous Kolebaba 1999, p. 9). Slender, orthocones with circular 12 initial constriction and inflation adoral of this constric- or compressed cross-section; aperture strongly oblique, 13 tion, and slightly oblique undulation. The specimen sloping adapically from antisiphuncular to prosiphuncu- 14 described here must remain in open nomenclature until lar side; aperture slopes more strongly on lateral sides 15 better material is available. and flattens near antisiphuncular and prosiphuncular 16 sides; ornamented with growth lines or weak ridges 17 parallel to aperture; sutures straight or slightly oblique, 18 Parasphaerorthoceras sp. H sensu Ristedt 1968. form shallow lateral lobes; septa moderately concave; 19 Plate 13, figure 4 siphuncle subcentral and siphuncular segments tubular; 20 septal necks orthochoanitic; episeptal, hyposeptal and 21 1968 Parasphaerorthoceras sp. H; Ristedt, p. 275, pl. 4, mural deposits occur. 22 fig. 9; pl. 5, fig. 7. 23 1977 Parasphaerorthoceras sp. H. Ristedt; Serpagli and Remarks. This genus differs from Protobactrites and Bogo- 24 Gnoli, p. 169, pl. 4, figs 11–15. slovskya in having a distinctively oblique, transverse orna- 25 mentation, but the apical characters of species assigned to 26 Material. 1 apical fragment, MB.C.9514, from limestone nodules it are poorly known. The only unquestionable apices of 27 in bed OP-M, Ludfordian; 3 apical fragments, MB.C.9521–23, Plagiostomoceras were figured by Dzik (1984, pl. 26, figs 28 from bed BS, Lochkovian; Filon Douze section. 1–2, 5); they are similar to Sphaerorthoceras beatum Rist- 29 edt, 1968, in having an initial chamber with a slightly 30 Description. MB.C.9514 is apical fragment 2.4 mm long; adapical smaller cross-section diameter than the subsequent conch 31 diameter 0.7 mm; adoral diameter 1.3 mm. Initial chamber not preserved. Adapical end of fragment represents first septum and directly adoral of the initial constriction. It is questionable 32 initial constriction. Conch cross-section slightly depressed. whether the apex figured by Dzik (1984, pl. 27, fig. 1) 33 Conch margins convex in median section. Surface ornamented and assigned to Plagiostomoceras cf. angustum (Holzapfel, 34 with straight, transverse undulations; seven undulations occur 1885) falls within the circumscription of the genus. The 35 within a distance of 1 mm. initial chamber of this apex is very short and resembles a 36 Three specimens from bed BS are complete, morphologically calotte, and the cross-section of the conch directly adoral 37 very similar, fragments of apical 2–3 mm of conchs. Initial of the initial constriction is larger than that of the initial 38 chamber 0.6 mm long, subspherical. At initial constriction first chamber. 39 septum occurs at conch height of 0.7 mm. Maximum inflation Plagiostomoceras is similar to Merocycloceras in conch 40 of subsequent conch section at 1.2 mm from tip where height shape and ornamentation, but the apex of the latter differs 41 is 1.2 mm. Conch cross-section depressed 2.5 mm from tip; in having several swollen first chambers. Because the apex 42 width to height ratio 1.3. Surface ornamented with straight, of many species of Plagiostomoceras is not known, the pos- 43 directly transverse undulation; ten undulations occur at dis- tance of 1 mm. sibility exists that several species conventionally assigned to 44 this genus may be more correctly assigned to Merocycloc- 45 Remarks. The size and shape of the conch and the eras. The adult growth stages of Hemicosmorthoceras are 46 transverse undulation of the fragments are characteristic indistinguishable from those of Plagiostomoceras but it has 47 of P. sp. H sensu Ristedt 1968, as recognized by Serpa- very conspicuous early growth stages. I assign conch frag- 48 gli and Gnoli (1977) who described details of the septal ments similar in shape and ornamentation to Hemicosmor- 49 neck and later growth stages. The reason why they thoceras, Merocycloceras and Plagiostomoceras to the last of 50 retained this form in open nomenclature is difficult to these genera when the apical shape is not known, or where 51 understand, but the poor preservation of the Filon it differs from known species of the first two. 52 Douze material does not justify the erection of a new 53 species here. Occurrence. Middle Ordovician–Early? Devonian; world-wide. 54 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 93

1 Plagiostomoceras pleurotomum? (Barrande, 1866) Diagnosis. Plagiostomoceras with slender shell and elliptical, 2 Plate 10, figure 11 compressed cross-section; angle of expansion 2–5 degrees; 3 conch surface ornamented with sharp, obliquely transverse 4 *1866–74 Orthoceras pleurotomum Barrande, pp. 412–413, lirae and shallow wide valleys; lirae imbricate with steep 5 587–588, 599, pl. 9, figs 21–23; pl. 224, figs 12–14; slope towards apex; they slope in adapical direction on 6 pl. 296, figs 1–24; pl. 366, figs 1–4. prosiphuncular side, forming wide shallow lobe on prosip- 7 1952 Plagiostomoceras pleurotomum (Barrande); Teichert huncular side and conspicuous saddle on antisiphuncular and Glenister, p. 741. 8 side; of four or five lirae only two span entire circumfer- 1962 Plagiostomoceras pleurotomum (Barrande); Balashov 9 and Zhuravleva, pl. 11, fig. 1. ence; the rest span only two-thirds of circumference, disap- 10 1999 Pleurostomoceras pleurotomum (Barrande); Kolebaba, pearing on antisiphuncular side; in juvenile shell all lirae 11 p. 9, pl. 3, figs 1–8; text-fig. 12d. reach around entire circumference; sutures oblique, parallel 12 2002 Pleurostomoceras pleurotomum (Barrande); Kolebaba, to ornamentation; septal distance 0.3–0.5 of conch height; 13 p. 184, text-fig. 2a. septal necks long, orthochoanitic; septal neck length greater 14 than diameter of septal perforation, which is c. 0.1 of 15 Material. 1 specimen, MB.C.9798, from nodules in OP-M, Lud- conch-cross-section; siphuncle eccentric. 16 fordian, Filon Douze section. 17 Description. Larger, well preserved fragment (MB.C.9944) 5 mm 18 Diagnosis. Plagiostomoceras with slender shell and elliptical, long, conch height 7.1–8.3 mm (angle of expansion 5 degrees), 19 compressed cross-section; ornamented with sharp, obli- adapical conch width 6.4 mm. Conch elliptically compressed 20 quely transverse ridges and shallow, wide valleys; ridges with width to height ratio of 0.9. Shell ornamented with imbri- 21 imbricate with steep slope towards apex; ridges slope in cate transverse lirae. At distance of 5 mm 12 oblique lirae occur on prosiphuncular side, forming conspicuous saddle on antisip- 22 adapical direction on prosiphuncular side, forming wide shallow lobe on prosiphuncular side and conspicuous sad- huncular side; here very faint, distance between them on antisip- 23 huncular side c. 1 mm (Pl. 10, fig. 13). Siphuncle eccentric. dle on antisiphuncular side; every second ridge spans only 24 Diameter of septal perforation 0.7 mm at most adoral septum. 25 two-thirds of circumference, disappearing on antisiphun- Septal distance c. 2 mm. 26 cular side; in juvenile shell all ridges reach around entire Smaller, well-preserved specimen (MB.C.10088) 21 mm long, 27 circumference; sutures oblique, parallel to ornamentation; with cross-section height 2.3–4.3 mm, adoral width 4 mm, rep- 28 septal distance 0.5–0.8 of conch height; septal necks long, resents juvenile growth stages with characteristic obliquely trans- 29 orthochoanitic; septal neck length greater than diameter of verse lirae spanning entire circumference (Pl. 10, fig. 17). Eight 30 septal perforation; diameter of septal perforation c. 0.1 of lirae occur at distance of 3 mm. Septal distance 1.6 mm at 31 conch-cross-section; siphuncle eccentric. adapical end of specimen. 32 33 Description. Fragment of phragmocone 24 mm long, dorsoven- Remarks. The diagnosis was compiled from the original 34 tral diameter 5.7 mm. Conch ornamented with distinctive obli- description and figures of Barrande (1866). Plagiostomoc- 35 que ridges with shallow valleys in between. Every second ridge eras bifrons resembles P. pleurotomum in general shell spans entire circumference, these spaced at c. 1–1.3 mm. Interca- 36 shape and ornamentation. However, in the latter species lated ridges occur at distance of 4 mm adoral of every second every second ridge spans the entire circumference and the 37 first order ridge. Distance between sutures 1.7 mm. 38 angle of expansion is lower. 39 Remarks. The diagnosis of this species is derived from the Occurrence. Lochkovian; Czech Republic and Morocco. 40 original description and figures of Barrande (1860–70). 41 MB.C.9798 displays the typical ornamentation of P. pleu- 42 rotomum, but the internal characters are not known. Plagiostomoceras culter (Barrande, 1866) 43 Plate 10, figures 9, 14, 18 44 Occurrence. Ludfordian–Lochkovian; Czech Republic and Morocco. 45 *1866–70 Orthoceras culter Barrande, pl. 239, figs 9–11, pl. 46 334, figs 5–22; pl. 442, figs 7–8. 47 Plagiostomoceras bifrons (Barrande, 1866) comb. nov. 1874 Orthoceras culter Barrande, p. 626. 48 Plate 10, figures 13, 17 1991 Plagiostomoceras culter (Barrande); Gnoli and 49 Serpagli, pp. 190, 194, pl. 3, fig. 6. 50 14 *1866 Orthoceras bifrons Barrande, p. ?, pl. 367, figs 1–31; 1999 Plagiostomoceras culter (Barrande); Histon and 51 pl. 442, figs 26–28. Gnoli, pp. 384, 388, tables 1–2. 52 53 Material. 2 specimens, MB.C.9944, 10088, from bed OJ-I; Loch- Material. 1 fragment, MB.C.9947, from OP-K, Ludfordian; more 54 kovian, Filon Douze section. than 100 specimens from bed PK, Lochkovian, Filon Douze section. 94 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Diagnosis. Plagiostomoceras with slender, nearly smooth Diagnosis. Plagiostomoceras with elliptically compressed 2 shell; compressed cross-section highly variable, from ellipti- cross-section and straight conch; angle of expansion c. 7 3 cal, egg-shaped to rounded triangular; ratio of conch width degrees; conch width to height ratio c. 0.8; ornamented 4 to height 0.65–0.75; ornamented with faint, irregularly with narrow, transverse undulation and faint longitudinal 5 spaced, oblique growth lines forming conspicuous saddle striae; undulations obliquely transverse, forming conspic- 6 on prosiphuncular side; sutures straight or very slightly uous lateral saddle, irregularly spaced, about six undula- 7 oblique, forming conspicuous lateral lobe; septal spacing tions occur within distance similar to conch height; 8 close at 0.2–0.4 of conch height; septal perforation <0.1 of sutures slightly oblique, sloping parallel to transverse 9 conch height in diameter; siphuncle eccentric. ornamentation; septal distance 0.5 of conch cross-section; 10 siphuncle eccentric. 11 Description. Specimen MB.C.9947, a fragment of three chambers 12 with adapical part of body chamber, is 34 mm long; conch Description. Holotype 14.5 mm long; conch height 6.8–8.6 mm; 13 height 19–21 mm; adoral width 19 mm. Height of each of the adoral width 7 mm; angle of expansion 7 degrees. Surface orna- 14 three chambers 2 mm. Sutures form shallow lateral lobe. Shell mented with irregularly spaced, narrow undulations and fine, 15 thickness at base of body chamber 0.3 mm. Faint thickening of shallow longitudinal striae. Striae between undulations highest shell of body chamber at distance of c. 16 mm from last septum 16 adapical of each undulation, giving shell an imbricated appear- forming shallow undulation on mould of chamber. Faint, irregu- ance. At distance of 10 mm seven oblique, transverse undula- 17 larly spaced growth lines form conspicuous saddle on one side tions, sloping in adoral direction on prosiphuncular side, form 18 of conch (Pl. 10, fig. 9). distinctive lateral saddle. Sutures slightly oblique, sloping in sim- 19 MB.C.9943, a fragment of five chambers with adapical part of ilar direction to transverse ornamentation. Septal distance c. 20 body chamber, is 40 mm long; conch height 20–23 mm; adoral 5 mm. Siphuncle eccentric. 21 width 19 mm (Pl. 10, fig. 18). Height of chambers 1.8–2.5 mm. 22 Most adoral two chambers narrowest. Sutures form shallow lat- Remarks. Plagiostomoceras gruenwaldti is ornamented 23 eral lobe. Length of body chamber 32 mm. Conch margins in with irregularly spaced narrow undulations that are more 24 median section slightly convex. At adoral end of fragment of closely spaced and less conspicuous than in other species body chamber shallow constriction occurs. 25 of the genus. 26 MB.C.9953 is fragment of body chamber and one septum, showing siphuncle, which is eccentric, at conch height 14.6 mm; 27 centre of septal perforation 6.1 mm from conch margin. Dia- 28 meter of septal perforation 1.3 mm. Plagiostomoceras reticulatum sp. nov. 29 Plate 10, figures 7–8 30 Remarks. The diagnosis of this species is based on the 31 original figures of Barrande (1860–70). Compared to his Derivation of name. Latin, reticulatus, net-like, referring to the 32 specimens, those from the Filon Douze section have a less ornamentation of this species. 33 variable cross-section, being invariably compressed ellipti- 34 cal; in some specimens it is egg-shaped with the siphuncle Holotype. MB.C.10116 (Pl. 10, figs 7–8). 35 on the narrower side of conch. 36 Type locality and horizon. Filon Douze section, bed OJ-I, Loch- kovian. 37 Occurrence. Ludfordian–Lochkovian; Czech Republic, Morocco 38 and Sardinia. 39 Other material. 8 specimens, MB.C.9638, 10110–15, 10131, from 40 the type locality and horizon. 41 Plagiostomoceras lategruenwaldti sp. nov. Diagnosis. Plagiostomoceras with slightly compressed cross- 42 Plate 10, figure 12 section and slightly bent, slender conch; angle of expansion 43 c. 3 degrees; ornamented with transverse ridges, sloping 44 Derivation of name. Latin, late, wide, referring to the transverse slightly in adoral direction on convex side of curvature of 45 ornamentation, which is similar to that of P. gruenwaldti (Bar- growth axis, forming shallow lateral lobe and distinctive 46 rande, 1868) but more widely spaced. saddle on this side of conch curvature; about ten ridges 47 within distance similar to conch cross-section; faint longi- 48 Holotype. MB.C.9954 (Pl. 10, fig. 12). tudinal striae form shallow reticulate pattern; sutures 49 slightly oblique, sloping parallel to transverse ridges; septal 50 Type locality and horizon. Filon Douze section, bed OJ-I, Loch- distance 0.4 of conch cross-section; siphuncle subcentral. 51 kovian. 52 Description. Holotype 14 mm long; conch height 5.7–6.3 mm; 53 Other material. 1 specimen, MB.C.9955, from the type locality and horizon. adoral width 5.6 mm; angle of expansion 2.5 degrees. Ten trans- 54 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 95

1 verse ridges occur within 5 mm. Ridges slightly oblique, sloping Description. MB.C.9945 51 mm long; dorsoventral diameter 2 in adoral direction on convex side of curvature of growth axis, 13.5 mm; conch width 12.5 mm with ten chambers. Cross-sec- 3 forming shallow lateral lobe and distinctive saddle on this side tion of fragment compressed oval, increases from 9.2 to 4 of conch curvature. Faint, shallow, longitudinal striae cross 13.5 mm in diameter. Conch surface smooth. Septal perforation 5 transverse ridges. Distance between longitudinal striae c. 1.4 mm wide at conch diameter of 12 mm. Septal necks 1.7 mm 0.3 mm. Siphuncle nearly central. Diameter of septal perforation long and funnel-like. 6 at most adapical septum 0.4 mm. Distance between septa c. 7 2 mm. Largest specimen (MB.C.10110) 14 mm long, cross-sec- Occurrence. Late Emsian–Givetian; Germany, Morocco, UK and 8 tion height 9–9.5 mm; angle of expansion 2 degrees, ratio of USA. 9 conch width to height 0.95. Variation of ornamentation and 10 conch shape very low in eight specimens known. 11 Bactrites?sp. 12 Remarks. This species resembles Orthoceras placidum Bar- Plate 13, figure 8 13 rande, 1868 (species combined Plagiostomoceras below: 14 see ‘List of new combinations’), which is similarly orna- Material. 1 apical fragment, MB.C.5764, from bed KMO-III, 15 mented with longitudinal striae, but the transverse ridges Pragian, Filon Douze section. 16 are clearly more oblique and possess conspicuous lateral 17 lobes. Description. Fragment 2.2 mm long, adoral diameter 0.5 mm; 18 very slightly bent. Initial 0.75 mm slightly inflated with maxi- 19 mum diameter of 0.45 mm. Shallow constriction adoral of 20 Order BACTRITIDA Shimansky, 1951 inflated part at distance 0.75 mm from tip where conch diame- 21 Family BACTRITIDAE Hyatt, 1884 ter is 0.4 mm. Interval adoral of constriction grows with angle 22 of expansion of 4 degrees. First chamber 0.55 mm high, second and third chambers 0.2 mm high. Subsequent chambers 0.25, 23 Genus BACTRITES Sandberger, 1843 0.35 and 0.5 mm high respectively, measured from apical direc- 24 tion adorally. 25 Type species. Bactrites subconicus Sandberger, 1843, from the 26 Wissenbach Slate, Eifelian of Wissenbach, Germany. Remarks. The entire specimen was ground successively 27 parallel to the longitudinal axis to locate the position of 28 Diagnosis (after Erben 1964, p. K501). Slender orthocones the siphuncle. During this process no siphuncle was 29 with nearly circular to broadly oval cross-section; sutures found although the individual septa were completely pre- 30 almost straight with small ventral lobe, on lateral sides served; there were no septal perforations in a central or 31 rectiradiate or prorsiradiate; growth lines form broad, subcentral position in the specimen. 32 shallow ventral sinus and low dorsal saddle. During the preparation of numerous median sections 33 of orthocones it was often extremely difficult to locate the 34 Occurrence. Pragian?–Permian; world-wide. siphuncular perforation of bactritoids because of their 35 marginal position and small diameter. It is concluded, 36 therefore, that the specimen is probably the apex of a 37 Bactrites gracile (Blumenbach, 1803) bactritoid and that the marginal septal perforation could 38 Plate 14, figure 12 not be seen during the grinding process. 39 40 * 1803 Orthoceras gracile Blumenbach, pl. 2, fig. 6. 41 2005 Bactrites gracile (Blumenbach); Kro¨ger et al., Genus DEVONOBACTRITES Shimansky, 1962 42 pp. 331, 339, fig. 1A. [with synonymy]. 43 Material. 3 specimens, MB.C.9538–39, 9545, from bed F, P. par- Type species. Orthoceratites obliquiseptatum Sandberger and 44 titus conodont Biozone, early Eifelian, Filon Douze section. Sandberger, 1852, from the Wissenbach Slate, Eifelian of Wissen- 45 bach, Germany. 46 15Diagnosis (from Kro¨ger and Isakar 2006, p. 339) . 47 Smooth, straight or very slightly bent Bactrites with circu- Emended diagnosis. Smooth, straight or very slightly bent 48 lar or compressed cross-section; sutures straight, slightly bactritoids with circular or compressed cross-section; 49 oblique; septal spacing variable with approximately two sutures oblique, sloping in adoral direction on prosiphun- 50 septa at distance similar to cross-section; initial chamber cular side; septal spacing close with c. 3–4 septa at dis- 51 ovate, smooth, with circular cross-section, c. 0.9 mm wide tance similar to conch cross-section; initial chamber 52 and 1.2 mm long; ovate shape of initial chamber highly elongate egg-shaped with acute tip and compressed cross- 53 variable. section. 54 96 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Remarks. Devonobactrites was erected with only the brief- 18 mm long, with maximum cross-section diameter of chamber c. 2 est of diagnoses: ‘Differs from Bactrites in having a more 7 mm. Septa slightly oblique, sloping adorally on prosiphuncular 3 sloped suture and shorter chambers’ (Shimansky 1962, p. side of conch. Obliquity of septa varies between specimens. Septal 4 236). Erben (1964, p. K503) questioned the ‘indepen- spacing 0.2–0.25 of conch cross-section (Pl. 14, fig. 7). In early 5 dence’ of the genus because of the high variability of the juvenile growth stages, angle of expansion very low and septal spacing more than 0.7 of conch cross-section. Sutures oblique, 6 diagnostic characters. Ignoring the discussion of the con- forming shallow lateral lobes and broad saddle on antisiphuncular 7 cept of ‘independence’ of a genus, I accept the genus and side. Siphuncle marginal and very narrow. 8 include the apical characters in the diagnosis. The apex of Apex (Pl. 13, figs 9–10) 0.6–0.84 mm long and 0.32–0.4 mm in 9 Devonobactrites obliquiseptatum differs considerably in size diameter (15 specimens measured). Diameter at initial constric- 10 and shape from that of Bactrites gracile. tion 0.32–0.36 mm (13 specimens measured). Conch adoral of 11 initial chamber nearly straight with very low angle of expansion 12 Occurrence. Early Emsian (Zlı´chovian)–early Eifelian; Germany and wide chamber distances. Septal perforation at initial septum 13 and Morocco. marginal. Cross-section of apical conch slightly compressed. 14 15 Remarks. The large quantity of material collected from 16 Devonobactrites obliquiseptatus (Sandberger and the Filon Douze section provides information on apical 17 Sandberger, 1852) and adult characters and intraspecific variation. All these 18 Plate 13, figures 9–10; Plate 14, figures 6–9 data are now included within the emendation of D. obliq- 19 uiseptatum. 20 * 1852 Orthoceras obliqueseptatum Sandberger and 21 Sandberger, p. 160, pl.18, figs 2, 2a–e. Occurrence. Early Emsian (Zlı´chovian)–early Eifelian; Germany 22 1876 Orthoceras oblique-septatum Sandberger and and Morocco. Sandberger; Maurer, p. 829. 23 1878 Orthoceras obliqueseptatum Sandberger and 24 Sandberger; Kayser, p. 81, pl. 20, fig. 18. Devonobactrites emsiense sp. nov. 25 1962 Devonobactrites obliquiseptatus (Sandberger and Plate 16, figures 1–2 26 Sandberger); Shimansky, p. 263, pl.1, fig. 6. 27 1964 Devonobactrites obliqueseptatus (Sandberger and Derivation of name. From Emsian, with reference to the type 28 Sandberger); Erben, p. K503, fig. 361, 2a–c. horizon. 29 2005 Bactrites sp. C; Kro¨ger et al., p. 334, figs 4A–B,5A. 30 2008 Devonobactrites obliqueseptatus (Sandberger and Holotype. MB.C.9531 (Pl. 16, fig. 1–2). 31 Sandberger); Klug et al., pp. 48–49, pl. 6, figs 11–12; pl. 7, figs 1–24. 32 Type locality and horizon. Filon Douze section, bed KMO-V, 33 Dalejian, late Emsian. 34 Material. 467 fragments of phragmocone and body chamber, MB.C.9542–47, 9568; 19 apices, MB.C.9548–49, 9550.1–17, from 35 bed EF, Zlı´chovian, Emsian, Filon Douze section. Other material. 3 specimens, MB.C.9535–37, from the Erbenoc- 36 eras Limestone, Zlı´chovian, early Emsian, Filon Douze section. 37 Emended diagnosis. Devonobactrites with compressed 38 cross-section, close septal spacing with approximately four Diagnosis. Devonobactrites with very slightly bent conch; 39 septa at distance similar to cross-section; angle of expan- angle of expansion c. 3 degrees; cross-section compressed 40 sion c. 5 degrees; cross-section of base of adult body cham- elliptical, with conch width to height ratio of c. 0.8; three 41 ber c. 5 mm; length of adult body chamber c. 20 mm; apex septa at distance similar to conch cross-section; suture 42 elongate egg-shaped with acute tip; faint constriction and straight or with very shallow lateral lobes, slightly oblique, 43 first septum at c. 0.6–0.9 mm from tip with diameter of sloping adorally on prosiphuncular side. 44 0.4 mm; diameter of initial conch 0.3–0.4 mm. 45 Description. Holotype 40 mm long, cross-section compressed elliptical, with conch height 11–13 mm and adoral conch width 46 Description. Conch nearly smooth with faint, oblique undulation 11.6 mm. Conch surface not preserved. Fragment has ten slightly 47 in late growth stages, which form lobe on prosiphuncular side. oblique septa that slope in adoral direction on prosiphuncular 48 Faint, oblique growth lines slope adapically on prosiphuncular side. Sutures straight or with shallow lateral lobe. 49 side parallel to the undulations. Conch grows constantly with MB.C.9535 is single chamber of phragmocone 3.9 mm long, 50 angle of expansion averaging 5 degrees (360 specimens measured; 13.5 mm high, 12 mm wide. Diameter of siphuncle 1.45 mm. 51 standard deviation 2.3 degrees). Cross-section ovate-compressed MB.C.9536 is 13.5 mm in maximum diameter and displays three with average width to height ratio of 0.89 (423 specimens mea- 52 16chambers with distance of 4.5 mm, and smooth surface of outer sured; standard deviation 0.12). Mature septal crowding occurs at 53 shell. 54 cross-section diameter of 3–4 mm. Mature body chamber c. 1 KRO¨ GER: NAUTILOIDS BEFORE AND DURING THE ORIGIN OF AMMONOIDS 97

1 Remarks. Devonobactrites emsiense resembles Bactrites au- 1933 Lobobactrites ellipticus (Frech); Schindewolf, p. 73, 2 savensis Steininger, 1853, from the Frasnian of Germany, pl. 3, figs 1, 7; pl. 4, fig. 8; text-fig. 15. 3 the cross-section of which, however, is less compressed and 1960 Lobobactrites ellipticus (Frech); Erben, pp. 17, 33, 4 the sutures have conspicuous lateral lobes. It differs from pl. 2, figs 2–3; text-fig. 5. 5 D. obliquiseptatum in having a less compressed cross-sec- 1984 Lobobactrites ellipticus (Frech); Dzik, p. 105, text-figs 39–40. 6 tion, slightly wider septal spacing and a larger adult size. 7 Material. 1 specimen, MB.C.9580, from bed F, P. partitus cono- 8 dont Biozone, Eifelian, Filon Douze section. 9 Devonobactrites sp. 10 Plate 14, figure 15 Diagnosis. Lobobactrites with narrowly compressed oval 11 cross-section; sutures with small ventral lobe, well-devel- 12 Material. 3 fragments of the body chamber, MB.C.10195–97, oped lateral lobes and dorsal saddle; surface smooth or from bed EF, Zlı´chovian, early Emsian, Filon Douze section. 13 with faint growth lines. 14 Description. MB.C.10195 is 11.6 mm long; cross-section height 15 Description. Fragment of phragmocone 39 mm long; conch 2.48–2.73 mm. MB.C.10196 is 18.6 mm long; cross-section 16 height 6.0–6.2 mm. Cross-section elliptically compressed; conch height 3.47–4.25mm. MB.C.10197 is 20.4 mm long; cross-section 17 width to height ratio 0.65; nine chambers with sutures that have height 6.9–7.6 mm. Conch of all three specimens compressed; 18 conspicious lateral lobes; septal spacing highly variable. conch height to width ratio 0.89–0.98 (smallest–largest frag- 19 ment). Sutures slightly oblique. 20 Remarks. When erected, L. ellipticus was not described 21 Remarks. These fragments differ from D. obliquiseptatum thoroughly. In the caption of a plate in the atlas of a text- 22 in having a significantly lower angle of expansion. It is book (Frech 1897) there is only a short note that the sip- 23 impossible to diagnose a new species on the basis of this huncle is marginal. Schindewolf (1932, 1933) described 24 material. and defined Lobobactrites but failed to provide a detailed 25 description of the species. Here, I regard L. ellipticus as a 26 Lobobactrites that shows the general characters of the 27 Genus LOBOBACTRITES Schindewolf, 1932 genus but lacks flattened lateral sides and carinae and has 28 a smooth shell. 29 Type species. Bactrites ellipticus Frech, 1897, from theWissenbach 30 Slate, Eifelian of Wissenbach, Germany. Occurrence. Wissenbach Slate, Eifelian; Germany, and P. partitus 31 conodont Biozone, Eifelian, Morocco. 32 Diagnosis (after Erben 1964, p. K501; Schindewolf 33 1933). Slender bactritoids with narrowly oval cross-sec- 34 tion; some forms have flattened lateral sides and rarely LIST OF NEW COMBINATIONS 35 dorsal carina; sutures with small ventral lobe, well-devel- 36 oped lateral lobes and dorsal saddle; growth lines similar Some of the species noted above under ‘Other species 37 to those of Bactrites but more strongly rursiradiate, dorsal included’ in a genus belong to different genera: they are 38 saddle more prominent and commonly pointed; initial referred to the genera to which they were originally 39 chamber elongate-ovate with circular cross-section, width assigned by their authors. Two are mentioned in different 40 of 0.9 mm and length of 1.5 mm. contexts and some are included in discussions. These taxa 41 are formally combined with the genera concerned here. 42 Occurrence. Emsian–Late Devonian; Australia; China; Germany, For the sake of completeness, the new combination of 43 Morocco, North America and Russia. Plagiostomoceras bifrons formally recorded above is 44 included in this list. 45 Ventrobalashovia altajense (Zhuravleva, 1979) comb. nov. 46 Lobobactrites ellipticus (Frech, 1897) Tripleuroceras altajense Zhuravleva, 1979, p. 305, pl. 6, figs 3–5. 47 Plate 14, figures 10–11 48 Orthorizoceras sinkovense (Balashov, in Balashov and Kiselev 49 1852 Bactrites carinatus Mu¨nst. sp.; Sandberger and Sand- 1968) comb. nov. 50 berger, p. 129, pl. 17, figs 3a–d,3f–n (non pl. 17, Metarizoceras sinkovense Balashov, in Balashov and Kiselev 1968, 51 fig. 3e). p. 15, pl. 3, fig. 4. * 1897 Bactrites ellipticus Frech, pl. 30a, fig. 7a–c. 52 Subormoceras dobrovljanense (Kiselev, in Balashov and Kiselev 53 1932 Lobobactrites ellipticus (Frech); Schindewolf, p. 174, text-fig. 5c. 1968) comb. nov. 54 98 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Ormoceras dobrovljanense Kiselev, in Balashov and Kiselev, p. 24, Angeisonoceras imminutum (Barrande, 1870) comb. nov. 2 pl. 3, fig. 2a–b. 22Orthoceras imminutum Barrande, 1870, p. ?, pls 373–375. 3 Subormoceras rashkovense (Kiselev, in Balashov and Kiselev 1968) Angeisonoceras inchoatum (Barrande, 1868) comb. nov. 4 comb. nov. 23Orthoceras inchoatum Barrande, 1868, p. ?, pl. 209, figs 8–12; pls 5 Ormoceras rashkovense Kiselev, in Balashov and Kiselev 1968, p. 368–369. 6 23, pl. 7, figs 1–3. 7 Angeisonoceras libens (Barrande, 1870) comb. nov. 8 Subormoceras skalaense (Kiselev, in Balashov and Kiselev 1968) 24Orthoceras libens Barrande, 1870, p. ?, pl. 387. 9 comb. nov. Ormoceras skalaense Kiselev, in Balashov and Kiselev 1968, p. 24, Angeisonoceras limatum (Barrande 1870) comb. nov. 10 25 pl. 7, figs 4–5. Orthoceras limatum Barrande 1870, p. ?, pl. 375. 11 12 Cancellspyroceras loricatum (Barrande, 1868) comb. nov. Angeisonoceras squamatulum (Barrande, 1868) comb. nov. 13 17Orthoceras loricatum Barrande, 1868, p. ?, pl. 275, figs 10–13, pl. Orthoceras squamatulum Barrande, 1868, p. 455, pl. 302, figs 8– 14 424, figs 5–8. 13. 15 Infundibuloceras mira (Zhuravleva, 1978) comb. nov. Plagiostomoceras bifrons (Barrande, 1866) comb. nov. 16 26 Bogoslovskya mira Zhuravleva, 1978, p. 59, pl. 3, fig. 13. Orthoceras bifrons Barrande, 1866, p. ?, pl. 367, figs 1–31; pl. 17 442, figs 26–28. 18 Infundibuloceras komiense (Zhuravleva, 1978) comb. nov. 19 Sinoceras komiense Zhuravleva, 1978, p. 49, pl. 1, figs 11–12. Plagiostomoceras placidum (Barrande, 1868) comb. nov. 27 20 Orthoceras placidum Barrande, 1868, p. ?, pl. 298, figs18–35; pl. Tibichoanoceras abditum (Kiselev, in Balashov and Kiselev 1968) 367, figs 19–21. 21 comb. nov. 22 Michelinoceras abditum Kiselev, in Balashov and Kiselev 1968, p. 23 10, pl. 1, fig. 4. 24 CONCLUSIONS 25 Tibichoanoceras riphaeum (Zhuravleva, 1978) comb. nov. 26 Sinoceras riphaeum Zhuravleva, 1978, p. 47, pl. 1, figs 3–7. The Ludfordian–Lochkovian section at Filon Douze is 27 Adiagoceras subnotatum (Barrande, 1868) comb. nov. composed of several hundred metres of thick silty clay- 28 18Orthoceras subnotatum Barrande, 1868, p. ?, pl. 307, figs 5–8. stones that are intercalated by three horizons containing 29 proximal tempestites and sandstones with a low diversity 30 Angeisonoceras consocium (Barrande, 1870) comb. nov. bivalve-orthocerid fauna. In contrast, the Pragian–Eifelian 19 31 Orthoceras consocium Barrande, 1870, p. ?, pls 372–373, 375, 378. section is composed of an alternation of silty marls and 32 Angeisonoceras davidsoni (Barrande, 1870) comb. nov. nodular crinoid-dacryonoconarid limestones that contain 33 20Orthoceras davidsoni Barrande, 1870, p. ?, pls 391–393, 445. a rich benthos of trilobites, rugose corals and gastropods. 34 In addition, condensed cephalopod limestones occur in 35 Angeisonoceras festinans (Barrande 1870) comb. nov. the Emsian and Eifelian that commonly contain superfi- 21 36 Orthoceras festinans Barrande 1870, p. ?, pl. 373. cially corroded shell fragments. At the base of the post- 37 38 39 40 41 EXPLANATION OF PLATE 16 42 Figs 1–2. Devonobactrites emsiense sp. nov.; MB.C.9531, holotype; bed KMO-V, Dalejian, Emsian. 1, lateral view; note the oblique 43 septation. 2, ventral view, slightly weathered, showing position and shape of septal perforations. 44 Fig. 3. Orthoceridae gen. et sp. indet.; MB.C.9913; bed KMO-V, Daleijan, Emsian; median section. 45 Figs 4, 7. Arionoceras aff. canonicum (Meneghini, 1857); MB.C.10229; bed OP-M, Ludfordian, Ludlow. 4, lateral view. 7, adapical view; 46 note comparatively strongly compressed conch. 47 Figs 5–6. Arionoceras capillosum (Barrande, 1867); MB.C.10206; bed BS, Lochkovian. 5, lateral view. 6, detail of lateral view; scale bar 48 represents 1 mm. 49 Fig. 8. Deiroceras hollardi sp. nov.; MB.C.9630; Deiroceras Limestone, Zlı´chovian, Emsian; detail of conch surface showing transverse 50 lirae; scale bar represents 1 mm. 51 Figs 9–11. Pseudendoplectoceras lahcani gen. et sp. nov.; MB.C. 10184, holotype; bed KMO-II, Pragian. 9, median section of entire 52 specimen. 10–11, showing the structure of the siphuncle and septal neck; note the recumbent septal necks and the 53 endosiphuncular deposits; scale bar represents 1 mm. 54 All specimens from the Filon Douze section and ·2 except where indicated by scale bar. PLATE 16 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 1 2 20 4 21 3 22 23 24 25 26 27 28 29 30 31 32 33 56 7 34 35 36 37 38 39 40 41 8 42 43 44 45 46 47 48 49 50 51 11 52 53 9 10 54 KRO¨ GER, nautiloids 100 SPECIAL PAPERS IN PALAEONTOLOGY, 79

1 Lochkovian limestone layers, there is often a horizon con- increasing taxonomic distinctness during the time interval 2 taining masses of dacryoconarids and large bivalves such concerned. However, a supra-regional comparison of this 3 as Panenka. pattern is currently impossible because the lack of data 4 Through the entire section no general tendency of for other regions. 5 increasing or decreasing depth of deposition can be deter- 6 mined. However, several depositional cycles occur. Some Acknowledgements. This work was financially supported by the 7 of these contain sandstones at their base (e.g. at top of Deutsche Forschungsgemeinschaft, DFG Grant KR 2095 ⁄ 2. I am 8 the Temperoceras limestone and Jovellania limestone suc- indebted to C. Klug (Zu¨rich, Switzerland), S. Lubeseder (Leices- 9 cessions), some display basal crinoidal-packstones (e.g. at ter, UK), and A. El Hassani (Rabat, Morocco) for help, advice 10 the top of the Scyphocrinites limestone succession), others and discussion of the stratigraphical part. I am grateful to A. El 11 contain winnowed crinoid-dacryonoconarid packstones at Hassani for logistical support of the field trips. Manina Lintz- meyer and Marek Damm (Berlin, Germany), and Mark Simon 12 the base (e.g. bed K2, Deiroceras Limestone). Transgres- (Hannover, Germany) helped in the preparation of the median 13 sive peaks are marked by horizons with phosphatic nod- sections and some of the illustrations. I thank Elke Sievert for 14 ules (bed PK) or limonitic concretions (e.g. bed EF) in preparing the hand drawings. I am grateful to the hospitality of 15 the siltstones, or by omission horizons at the top of cri- the family of Filon Douze miner L. Caraoui (Hassilbid, Tafilalt). 16 noid-dacryonoconarid pack- and wackestones (e.g. top of I thank M. Stenzel for mechanical preparation of the apices and 17 the Deiroceras Limestone). The condensed cephalopod S. Kiel (Leeds, UK) in joining me on my first field trip to Mor- 18 limestones of the Erbenoceras Limestones, of bed PI and occo in the spring of 2003. I am grateful for E. Shubert (Lon- 19 PII, are interpreted in terms of relatively shallow deposi- don, UK) for initial linguistic review of the manuscript. I am 20 tional settings close to, or above, storm wave-base (com- indebted to P. D. Lane (Keele, UK) for considerable editorial 21 pare Wendt et al. 1984). and scientific advice during preparation of the revised version of 22 A major facies change at the top of the Jovellania this paper, and to D. J. Batten (Manchester, UK) for his editorial 29work. The paper is a contribution to IGCP Project 497, ‘The 23 Limestones from dark tempestitic facies towards light- Rheic ocean: its origin, evolution and correlatives’. 24 coloured crinoid-dacryonoconarid limestones to marl 25 alternations is interpreted to coincide with the pesavis- 26 Event in the latest Lochkovian. This facies change does REFERENCES 27 not reflect a lasting sea-level drop at Filon Douze. The 28 post-Lochkovian sediments are considered to reflect on AGASSIZ, J. L. R. 1847. Nomenclator Zoologicus. Fasciculus 29 average depths of deposition similar to those of the XII. Indicem Universalem. Nomenclatoris Zoologici Index Uni- 30 pre-Pragian sediments. 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Complete list of occurrences of non-ammonoid cephalopods from the Filon Douze section, Tafilalt, Morocco

Species OP ⁄ OSP Deiroc. Erben. OP-M I-II* PK OJ-I BS OJ-II CK* KMO -I KMO -II KMO -III EF Lst. KMO -IV* Lst. KMO -V* F I+II P I+II

Pseudendoplectoceras lahcani 10 gen. et sp. nov. Brevicoceras magnum 1 gen. et sp. nov.

Cerovoceras fatimi 1 KRO gen. et sp. nov. ¨

Cerovoceras brevidomus 1 AMMONOIDS OF ORIGIN THE DURING AND BEFORE NAUTILOIDS GER: gen. et sp. nov. Jovellania cheirae sp. nov. 8 1 Bohemojovellania 2 bouskai Manda, 2001 Bohemojovellania adraei sp. 5 nov. Bohemojovellania 3 obliquum sp. nov. Ankyloceras sp. 1 Ventrobalashovia 1 zhuravlevai gen. et sp. nov. Mutoblakeoceras inconstans 1 gen. et sp. nov. Tafilaltoceras adgoi 1 gen. et sp. nov. Indet Nothoceratidae sp. A 1 Orthorizoceras desertum 1 gen. et sp. nov. Centroceras sp. 1 Ormoceras sp 1 Deiroceras hollardi sp. nov. 5 Metarmenoceras fatimae 3 sp. nov. Geidoloceras ouaoufilalense 11 gen. et sp. nov. Neocycloceras? termierorum 12 sp. nov. Probatoceras? sp. 1 Subdoloceras tafilaltense 1 gen. et sp. nov. 107 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

Appendix Continued. 108

OP ⁄ OSP Deiroc. Erben. 79 PALAEONTOLOGY, IN PAPERS SPECIAL Species OP-M I-II* PK OJ-I BS OJ-II CK* KMO -I KMO -II KMO -III EF Lst. KMO -IV* Lst. KMO -V* F I+II P I+II

Subdoloceras atrouzense 31 gen. et sp. nov. Subdoloceras engeseri 115 gen. et sp. nov. Subormoceras erfoudense 23 gen. et sp. nov. Subormoceras rissaniense 11 gen. et sp. nov. Subormoceras sp. 1 Spyroceras cyrtopatronus 2 sp. nov. Spyroceras fukuijense? Niko, 2 1996 Spyroceras latepatronus 3 sp. nov. Spyroceras patronus 11 (Barrande, 1866) Spyroceras? sp. A. 1 Spyroceras? sp.B. 1 Cancellspyroceras loricatum 2 (Barrande, 1868) Diagoceras sp. 1 Suloceras longipulchrum 3 sp. nov. Arthrophyllum vermiculare 15 37 58 14 6 4 4 1 1 (Termier and Termier, 1950) Sphooceras truncatum 5 Barrande, 1860 Chebbioceras erfoudense Klug 10 et al., 2008 Infundibuloceras brevimira 61 Klug et al., 2008 Infundibuloceras 11 longicameratum sp. nov. Infundibuloceras mohamadi 4 sp. nov. Kopaninoceras? jucundum 2 (Barrande, 1870) 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 1

Kopaninoceras? dorsatoides 78 sp. Nov Kopaninoceras thyrsus 80 2 (Barrande, 1870) Kopaninoceras? sp. 3 Merocycloceras sp. A 1 Merocycloceras sp. B 4 Merocycloceras? sp. C 1 Michelinoceras sp. 2 Orthocycloceras? fluminense 41 (Meneghini 1857) KRO Orthocycloceras tafilaltense 311 sp. nov. ¨ E:NUIOD EOEADDRN H RGNO AMMONOIDS OF ORIGIN THE DURING AND BEFORE NAUTILOIDS GER: Pseudospyroceras reticulum 1 gen. et sp. nov. Theoceras filondouzense 3 gen. et sp. nov. Tibichoanoceras tibichoanum 1 gen. et sp. nov. Orthoceratidae gen. 1 et sp. indet. Arionoceras canonicum 188 (Meneghini, 1857) Arionoceras aff. canonicum 65 (Meneghini, 1857) Arionoceras capillosum 25 (Barrande, 1867) Arionoceras sp. A 7 Adiagoceras taouzense 177 1 gen. et sp. nov. Parakionoceras originale 421 1 (Barrande, 1868) Anaspyroceras sp. 1 Indet. Dawsonoceratidae 1 Angeisonoceras reteornatum 5 gen. et sp. nov. Temperoceras? ludense 66 (Sowerby, in Murchison 1839) Temperoceras aequinudum 21027938 sp. nov. Temperoceras migrans 24 2 3 1 3 (Barrande, 1868) 109 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

Appendix Continued. 110

OP ⁄ OSP Deiroc. Erben. 79 PALAEONTOLOGY, IN PAPERS SPECIAL Species OP-M I-II* PK OJ-I BS OJ-II CK* KMO -I KMO -II KMO -III EF Lst. KMO -IV* Lst. KMO -V* F I+II P I+II

Kionoceras? doricum 4 (Barrande, 1868) Sichuanoceras zizense 2 sp. nov. Sphaerorthoceras sp. A 1 Sphaerorthoceras sp. B 1 Akrosphaerorthoceras sp. 1 3 Hemicosmorthoceras aichae 1 sp. nov. Hemicosmorthoceras 12280 4 semimbricatum Gnoli, 1982 Parasphaerorthoceras sp. B 1 sensu Ristedt 1968 Parasphaerorthoceras sp. G 1 sensu Ristedt 1968 Parasphaerorthoceras sp. H 13 sensu Ristedt 1968 Plagiostomoceras 1 pleurotomum? (Barrande, 1866) Plagiostomoceras bifrons 2 (Barrande, 1866) Plagiostomoceras culter 1 100 (Barrande, 1866) Plagiostomoceras 2 lategruenwaldti sp. nov. Plagiostomoceras reticulatum 9 sp. nov. Bactrites gracile 3 (Blumenbach, 1803) Bactrites? sp. 1 Devonobactrites 486 obliquiseptatum (Sandberger and Sandberger, 1852) Devonobactrites emsiense 31 sp. nov. Devonobactrites sp. 3 Lobobactrites ellipticus 1 (Frech, 1897)

Total number of specimens 442 16 103 318 36 3 6 84 127 42 560 5 10 16 6 15 7 Author Query Form

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Query reference Query Remarks 1 Au: Please amend ⁄ approve the suggested short title. 2 Au: Gabbot 1999 has been changed to Gabbott 1999 so that this citation matches the list. 3 Au: Chlupa`cˇ 1985 has been changed to Chlupa´c 1985 so that this citation matches the list. 4 Au: Ferretti et al. 1999 has been changed to Ferreti et al. 1999 so that this cita- tion matches the list. 5 Au: Please check the phrase ‘within’ here. 6 Au: ‘Kayser, 1887’ has been changed to ‘Kayser, 1878’. Please check. 7 Au: Please provide publication details for Kro¨ger (2006). 8 Au: Please check the phrase ‘within’ here. 9 Au: ‘Miller 1831’ has been changed to ‘Miller 1931’. Please check. 10 Au: Please check the phrase ‘within’ here. 11 Au: Please check the phrase ‘within’ here. 12 Au: Please check the phrase ‘at length’ here. 13 Au: Please check the phrase ‘within’ here. 14 Au: Please provide page range here. 15 Au: Kro¨ger et al. 2006 has been changed to Kro¨ger and Isakar 2006 so that this citation matches the list. 16 Au: Please check the phrase ‘with distance of’ here. 17 Au: Please provide page range here. 18 Au: Please provide page range here. 19 Au: Please provide page range here. 20 Au: Please provide page range here. 21 Au: Please provide page range here. 22 Au: Please provide page range here. 23 Au: Please provide page range here. 24 Au: Please provide page range here. 25 Au: Please provide page range here. 26 Au: Please provide page range here. 27 Au: Please provide page range here. 28 Au: Chlupa´cˇ 2000 has been changed to Chlupa´c et al. 2000 so that this citation matches the list. 29 Au: Please check the acknowledgement here. 30 Au: Please provide publisher name in reference Babin 1966 31 Au: Barrande (1877) not cited. Please cite reference in text or delete from the list. 32 Au: Please check the website address and confirm that it is correct throughout article. 33 Au: Comaschi (1949) not cited. Please cite reference in text or delete from the list. 34 Au: Kiselev et al. (1987) not cited. Please cite reference in text or delete from the list. 35 Au: Please check page range in reference Klug et al. 2008 36 Au: Please provide page range for reference Kro¨ger et al. 2008. 37 Au: Sandberger (1845) not cited. Please cite reference in text or delete from the list. 38 Au: Shimansky (1972) not cited. Please cite reference in text or delete from the list. 39 Au: Please check author name in reference Talent et al. 1993. 40 Au: Tshernyshev (1885) not cited. Please cite reference in text or delete from the list. 41 Au: Turek (1994) not cited. Please cite reference in text or delete from the list. 42 Au: Walliser (1996) not cited. Please cite reference in text or delete from the list. 43 Au: Menengini, 1857 has been changed to Meneghini 1857 so that this citation matches the list. MARKED PROOF Please correct and return this set

Please use the proof correction marks shown below for all alterations and corrections. If you wish to return your proof by fax you should ensure that all amendments are written clearly in dark ink and are made well within the page margins.

Instruction to printer Textual mark Marginal mark Leave unchanged under matter to remain Insert in text the matter New matter followed by indicated in the margin or Delete through single character, rule or underline or or through all characters to be deleted Substitute character or substitute part of one or through letter or new character or more word(s) through characters new characters Change to italics under matter to be changed Change to capitals under matter to be changed Change to small capitals under matter to be changed Change to bold type under matter to be changed Change to bold italic under matter to be changed Change to lower case Encircle matter to be changed Change italic to upright type (As above) Change bold to non-bold type (As above) or Insert ‘superior’ character through character or under character where required e.g. or

Insert ‘inferior’ character (As above) over character e.g. Insert full stop (As above) Insert comma (As above) or and/or Insert single quotation marks (As above) or

or and/or Insert double quotation marks (As above) or Insert hyphen (As above) Start new paragraph No new paragraph Transpose Close up linking characters

Insert or substitute space through character or between characters or words where required

Reduce space between between characters or characters or words words affected

   

   

                  
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