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