Bollettino della Società Paleontologica Italiana Modena, Novembre 1999

A septimembrate apparatus model for the Ordovician genus Cornuodus Fahraeus, 1966

Anita LOFGREN Department of Geology Lund University

KEYWORDS- , Cornuodus, Apparatus reconstruction, Ordovician.

ABSTRACT- An investigation o( the Ordovician conodont genus Cornuodus, based on the literature and a collection of almost 8,000 elements /Tom Swedish sections, has led to the conclusion that its apparatus is septimembrate with Pa, Pb, Sa, Sb, Se, Sdl and Sd2 elements. All previously described Cornuodus forms are referred to a single species, C. longibasis, but diffirent ecomorphotypes can be distinguished. The species has an extensive stratigraphical range, from the Tremadoc into the Ashgill. Its environmental preferences are discussed and the element types are described in detail.

RIASSUNTO- [Un modello septimembrato per l'apparato dei conodonti ordoviciani del genere Cornuodus]- L'analisi dei dati noti in letteratura e di una collezione di quasi ottomila elementi provenienti dalla Svezia ha portato alla conclusione che l'apparato del genere Cornuodus era costituito da sette elementi; infatti, sono stati individuati gli elementi Pa, Pb, Sa, Sb, Se, Sdl ed Sd2. Tutte le forme Iii Cornuodus precedentemente descritte vengono attribuite alla stessa specie, C. longibasis, tuttavia è possibile distinguere numerosi morfotipi. La specie ha una distribuzione stratigraflca molto ampia, dal Tremadoc all'Ashgill. Vengono presentate considerazioni paleoecologiche e descritti i singoli morfoelementi.

INTRODUCTION Pander, 1856, although the types of apparatus of these genera seem to differ slightly from that of Cornuodus. The genus Cornuodus was established by Fahraeus (1966) for coniform elements with an erect, laterally compressed cusp and a comparatively long, cylindrical SECTIONS AND MATERIAL base without costae or edges. As type species he chose the new species, Cornuodus erectus, the name being The materia! on which this investigation is based considered to be a subjective junior synonym of was mainly collected for biostratigraphical purposes, Drepanodus longibasis Lindstrom, 1955, by Lofgren and most of the faunas to which the Cornuodus (1978) and most subsequent authors. Serpagli (1967) elements belong have been described previously. and Dzik (1976) distinguished some later forms of the Cornuodus is found sparsely in most of my samples genus, but ali these can be regarded as modifìcations collected from mainland and fairly often within the septimembrate apparatus mode! of C in samples from Oland. In samples from shallower longibasis presented here. Thus C. longibasis seems to platform settings in Baltica, e.g. from the Tamsalu drill- beone of the longest-ranging Ordovician species (Text- core (north-central Estonia) frequencies of Cornuodus fìg. l), occurring in beds from the Tremadoc an d imo only rarely reach l o/o (Lofgren, undescribed collection). the Ashgill, although there are forms with an aberrant In some deeper settings, such as those investigated by morphology, for instance specimens with a particularly Rasmussen (1991, 1994) in western Jimtland and in long base. Since the long-based morphotypes occur in Norway, Cornuodus also seems to be rare. some of both the oldest and the youngest beds The elements of Cornuodus that were available to containing Cornuodus, these populations cannot be me for the investigation come from Gillberga distinguished as representing a separate, temporally and Sandvrk on Oland; Orreholmen, Gullhogen and distinct species, but are here treated as ecomorphotypic. Hallekis in Vastergotland; Gymninge, Lanna and Cornuodus has been reported from many areas and Hallabrottet in Narke; Finngrundet in the Gulf of seems to have lived in ali but the shallowest or most Bothnia; Sjurberg, Ravanas, Kargarde, Talubacken, isolated parts of the Ordovician seas. The distribution Nusnas, Fjacka and Leskusanget in Dalarna (for of Cornuodus in different biofacies types has also been locations of these sections, see Lofgren, 1995), and from reviewed; i t was apparently most common at medium the sections in Jamtland previously described by depths, and shows co-variation with Protopanderodus Lofgren (1978, 1993a). rectus in at least some environments. Ali my specimens are derived from limestones that This, together with other considerations, has led have been treated with acetic acid. The materia! on me to regard Cornuodus as being most closely related which calculations of element ratios, etc. have been to Protopanderodus Lindstrom, 1971 an d to Drepanodus based, has been retrieved by the buffering technique 176 A. LOFGREN

Conodont Zones and Typical Cornuodus Scalpellodus which, however, have a more complicateci Series, stages Subzones morphotypes microornamentation extenciing on to the base, anci a

Porkuni A. ordovicicus Zone thicker basai cavity wall. Ashgill l The olciest reporteci elements of Cornuodus are from l l A. superbus Zone the Tremacioc Paltodus deltifer Zone at Sjurberg anci l . Fjacka in Dalarna (Lofgren, 1994) anci Orreholmen Caradoc l A. tvaerensis Zone . l in Vastergodanci (Lofgren, 1996, fig. 4). Cornuodus l P. anserinus Zone elements from the upper Tremacioc "Scalpellodus" tersus Uhaku 6 ---- Zone in northern China (An et al., 1983) may be of lasnam. P serra Zone equivalent age or slighdy younger. This suggests that Aseri upper E. suecicus Zone the first appearance of Cornuodus is stratigraphically olcier than that of Protopanderodus, the olciest reporteci Llanvirn lower E. suecicus Zone fincis of which come from the uppermost Tremacioc E. ? variabilis- Paroistodus proteus Zone in Swecien (Protopanderodus Kunda M. ozarkodel/a Sz. (6 sp. in a sample from Sjurberg, Dalarna, Lofgren, 1994) E. ? variabilis· anci the uppermost Tremacioc - lower Arenig in M. parva Subzone ---- Argentina (P.leonardii, Serpagli, 1974); see also Lehnert M. parva Zone ( 199 5). The olciest une q uivocal recorcis of Scalpellodus l are also probably younger than those of Cornuodus. P. originalis Zone Bagnoli & Stouge ( 1997) founci Scalpellodus cf S. latus Volkhov n jusr below the first occurrence of Arenig B. navis Zone triangularis in the Horns Ucicie quarry section, anci the ·.\_ _..., B. triangularis Zone taxon also occurs more frequendy in other sections r---- somewhat higher up in the Volkhov (e.g. in the O. evae Zone Finngrunciet core, Lofgren, 1985). Cornuodus thus Latorp P elegans Zone represents a remarkably olci conociont lineage, almost rivalling genera such as Drepanodus, Paroistodus anci upper Paltodus in geologica! age. Cornuodus is also long- Paroistodus - proteus middla ranging, sin ce the stratigraphically youngest specimens Zone - Tremadoc come from the Ashgill (in the Carnic Alps, Serpagli, lower (upper part) 1967). upper Since only one species of Cornuodus can be P. deltifer Zone recognizeci with certainty (see uncier Systematic Palaeontology), it is impossible to make generalizations Text-fìg. l - Stratigraphic column and range of Cornuodus. about the morphology of element types apart from those of C. longibasis. A short ciescription of these element types will suffice here (see Plate l); further ciescribeci by Jeppsson et al. (1985). In the whole of particulars appear uncier Systematic Palaeontology. the collection of Cornuodus, except the c. 300 Pa element - Recurveci, with shortest base of all specimens from Jimdanci, the Color Alteration lnciex elements. Tenciency to cievelop a quasi-hook anterio- values (CAI, see Epstein et al., 1977) lie below 1.5, basally. Typifieci by the type specimen of C. bergstroemi that is, the specimens are virtually unaltereci, anci they Serpagli. are also otherwise well to extremely well preserveci. Pb element- Usually erect with the base longer than in The specimens illustrateci are kept in the Type the Pa element. Ecige cievelopeci anteriorly at l:iase-cusp Collection of the Department of Geology, Lunci ben ci. University, Lunci, Swecien. Sa and Sb elements - Erect to slighdy proclineci with long, narrow base. Sb element slighdy asymmetrical e. g. in position of posterior ecige of cusp. GENERAL CHARACTERISTICS OF CORNUODUS Se element - Erect to reclineci with fairly sharp base- cusp benci anci base somewhat abrupdy wiciening Elements of Cornuodus are coniform anci posteriorly. characterizeci by a laterally comrresseci cusp an ci a long Sd elements- Usually erect, sometimes slighdy recurveci base with a thin basai cavity wal . Microornamentation or proclineci with long narrow base, twisteci in relation is usually restricteci to the posterior margin of the cusp to cusp. In Sci l elements the base is shorter anci wicier anci consists of faint longituciinal striae. In this, the than in Sci2 elements. elements resemble those of Protopanderodus, a relateci The apparatus architecture of Cornuodus is probably genus with more robust elements. Elements of closer to that of Protopanderodus than to that of Cornuodus are sometimes mistaken for those of Scalpellodus. In Protopanderodus the elements with Pa SEPTIMEMBRATE CORNUODUS 177 and Sd positions resemble those in Cornuodus, while that I distinguish a distinct Pb (oz) element, which in Scalpellodus the P elements differ considerably Dzik (1994) neither described nor illustrateci, although morphologically. O n the basis of slighdy different data there is brief mention of an oz element in the text. Armstrong (1997) also suggested a closer relationship between Cornuodus and Drepanodus than between either of these genera and Scalpellodus. ELEMENT RATIOS

Since Cornuodus is uncommon or rare in most of APPARATUS RECONSTRUCTIONS IN CORNUODUS my samples this makes the calculation of element ratios difficult. However, five samples from Gillberga an d o ne Originally only o ne element type was distinguished, from Kargarde, each yielding from 173 to 562 probably because elements of Cornuodus are rare in specimens of Cornuodus, make up the basis for a most samples. For instance, Lindstrom's (1955) tentative reconstruction of the absolute number of description of Drepanodus longibasis was based o n only elements in each apparatus. The figures that fit most 12 specimens from 8 samples, and Fahraeus (1966) of the samples best are 4Pa, 4Pb, l Sa, 4Sb, 4Sc, 4Sdl described Cornuodus erectus on 20 specimens from 2 and 2Sd2 (23 elements in ali). In two of the samples samples, though he observed some variation in the 8Sb is closer to the acrual counts. Sa elements tend to development of posterior costae on the cusp in his be overrepresented, but only in one of the six specimens. Serpagli (1967) recognized 5 taxa which investigated samples is the ratio dose to 2Sa. Assuming are here treated as conspecific with C. longibasis. He that there was only a single Sa element in each animai, regarded two ofhis new species, Cornuodus bergstroemi the total number of elements in the Cornuodus an d C. montanaroe (specimens redrawn h ere as P l. l, apparatus (between 21 and 27) appears to be higher fig. l and fig. 4, respectively) as possibly conspecific, than has been calculated for other coniform thus being the first to tentatively suggest the existence apparatuses. Estimations for other coniform genera are: of different element types in Cornuodus. 17 elements in Panderodus (Sansom et al., 1995), 17 Lofgren (1978) proposed that there were at least in Paltodus (Lofgren, 1997b), 17 in Paroistodus three element types in C. longibasis, two "symmetrical" (Lofgren, 1997a), 17 or 15 in Semiacontiodus (Lofgren, (=Sa+Sb and Pb elements here), and one asymmetrical 1999). Noteworthy is that the characteristic Pa and (=Sd elements here). Since I had found no specimens Pb elements in Cornuodus seem to have been with the morphology of C. bergstroemi in my sparse represented by two pairs each in most of my collections. coliections from the oldest part of the Jamtland If these element types are indeed overrepresented (as sequence under investigation at that rime, I then treated they may weli be), the lower figure (21) is the more C. bergstroemi as a separate species (Lofgren, 1978). In probable. the Catalogue of Conodonts, Lindstrom (1981) correctly stated that elements morphologicaliy resembling the types of C. longibasis an d C. bergstroemi ENVIRONMENT (=Sb and Pa elements) coexisted throughout the Ordovician. Moreover, he recognized at least three Cornuodus has been retrieved from a great number element types within C. longibasis, on the basis of of areas where Ordovician rocks are preserved: Sweden Lofgren's (1978) descriptions. Stouge (1984), Stouge (Lindstrom, 1955; Fahraeus, 1966; van Wamel, 1974; & Bagnoli (1990) and Zhang (1998) also included Lofgren, 1978, 1994), Poland (Dzik, 1976, 1994), the elements earlier described as C. bergstroemi in C. Carnic Alps in N ltaly (Serpagli, 1967), Korea (Lee, longibasis. Dzik (1990, fig. 12, 1991, fig. 5A, B) 1970), S China (An, 1981; An et al., 1985; Ni & Li, distinguished two successive species of Cornuodus in 1987; Chen & Zhang, 1989; Ni et al., 1991; Zhang, the M6jcza section in Poland; in the lower part C. 1998), marginai parts of N China (An et al., 1983; longibasis (most of the elements with a comparatively An & Zheng, 1990), centrai Australia (Cooper, 1981), short base) and higher up in the section C. bergstroemi Newfoundland (Stouge, 1984; Stouge & Bagnoli, (most of the elements with an extremely long base), 1988), New York State (Landing, 1976), and from and illustrateci a pentimembrate apparatus for each Argentina (Serpagli, 1974; Lehnert, 1995; Albanesi, species. Later he further developed an appararus 1998). Thus during the Ordovician Cornuodus seems concept for Cornuodus (Dzik, 1994), that agrees with to have been present in ali but a few marine areas; i.e. that presented here in severa! criticai aspects. We thus it is lacking only in typical North American agree on the identification of the Pa and Se elements Midcontinent faunas and the Siberian and N Chinese and probably also on the Sa and Sb elements. I regard counterparts. Bagnoli & Stouge (1991) placed the M (ne) element distinguished by Dzik (1994, fig. Cornuodus in the "cold water group" in their 4) as o ne of the Sd elements in my reconstruction and palaeogeographic analysis. maintain that the M element is lacking in the In the biofacies analysis presented by Rasmussen Cornuodus apparatus. Another probable difference is & Stouge (1995) Cornuodus is not included, 178 A.L6FGREN presumably because the genus is rare in most Ansella and locally high frequencies of C. longibasis. environments, though it has a characteristic and Ansella (then = Belodella) was considered to be a shelf interesting pattern of occurrence. In some stratigraphic taxon (i.e. from fairly shallow water) by Barnes & intervals that I have investigated, such as the Volkhov Fahraeus (1975), but my observations point rather to to Kunda sequence at Lanna (Lofgren, 1995), the late open oceanic influences. In her biofacies smdy from Volkhov to early Kunda part of the Gillberga section, the Cow Head Group, Newfoundland, Pohler (1994, and the lower (Volkhov) part of the Kl.rgarde sequence, p. 22) found that in sediments of an age comparable C. longibasis varies according to a pattern resembling to those a t Gillberga Anse ila was restricted to the shelf that of Protopanderodus rectus. The relative numbers of edge. C. longibasis, however, are generally lower than those Only nine of all investigated samples yielded more of P. rectus and in its element frequency diagrams the than 4% of Cornuodus (maximum 13% in the top amplitude is accordingly narrower. When the relative sample from the Lanna quarry). In the sections at values of Protopanderodus rectus lie below 5% Cornuodus Ravanas, Lanna, and Hallekis the maximum relative may be lacking (as in the middle part of the Kargarde frequency of Cornuodus is encountered in the lower, section and in much of the Tamsalu core, Estonia). though no t the lowermost, part of the E.? variabilis Relative values of Protopanderodus calceatus Bagnoli & Zone, while at Gillberga, Gullhogen and Kargarde the Stouge, 1997 (previously referred to as P. cf. P. maximum frequency is found in the E.? variabilis - M. varicostatus by many authors) appear to be unrelated ozarkodella Subzone. At Hallekis (the westernmost to those of Cornuodus. In younger beds the combined section investigated) there is also an earlier maximum relative frequency of P. parvibasis, P. graeai and P. (5.3%) in the lower M. parva Zone. robustus vari es in apparently the same way as that of C. longibasis, e.g. in the upper (Kunda) part of the Kargarde sequence. SYSTEMATIC PALAEO TOLOGY Cornuodus longibasis and Drepanodus arcuatus co- occur and vary in a similar manner throughout much Genus CORNUODUS Fahraeus, 1966 of the sequence (Volkhov to upper Kunda) at Gullhogen (Skovde). A t Gillberga the mode of Type species- Cornuodus erectus Fahraeus, 1966 (= occurrence of D. arcuatus also somewhat resembles that Drepanodus longibasis Lindstrom, 1955). of C. longibasis, though the similarity is greater between C. longibasis and P. rectus. Comments - Lofgren (1978) treated the name C. In the upper third (upper Kunda) of the Gillberga erectus as a subjective junior synonym of D. longibasis, section there is a connexion between the occurrence of as have also most subsequent authors.

EXPLANATION OF PLATE l

Figs. 1-21 - Cornuodus longibasis (Lindsrriim, 1955). Al! xl05. 1-7 from rhe Upper Ordovieian of rhe Carnie Alps (redrawn from Serpagli, 1967). l) Pa elemenr (=Cornuodus bergstroemi n. sp. of Serpagli; Pl. 12, fig. 2b). 2) Sb? elemenr (=Cornuodus erectus Hhraeus of Serpagli; Pl. 12, fig. 5b). 3) Pb? elemenr (=Drepanodus sp. of Serpagli; Pl. 15 , fig. 6a). 4) Sa? elemenr (=Cornuodus montanaroae n. sp. of Serpagli; Pl. 12, fig. 4a). 5) Sd l? elemenr (=Scandodus? lanzaensis n. sp. of Serpagli; P l. 26, fig. 6a). 6) Se elemenr (=Scandodus? lanzaensis n. sp. of Serpagli; Pl. 26, fig. 4a). 7) Sd2 elemenr (=Scandodus? lanzaensis n. sp. of Serpagli; Pl. 26, fig. 7b; holorype). 8-14 - long-based popularion from rhe Baltoniodus triangularis Zone, sample HK89-0, Hallekis quarry, Vasrergiidand. 8) Pa elemenr, LO 7906r. 9) Pb elemenr, LO 7907r. lO) Sa elemenr, LO 7908r. 11) Sb elemenr, LO 7909r. 12) Sdl elemenr, LO 7910r. 13) Se elemenr, LO 7911 r. 14) Sd2 elemenr, LO 7912r. 15-21 -elemenrs from rhe Eoplacognathus? variabilis - parva Subzone (probably= lower Dzikodus tablepointensis Zone ofZhang, 1998), sample Ra5, Ravanas quarry, Dalarna. 15) Pa elemenr, LO 7913r. 16) Pb elemenr, LO 7914r. 17) Sb elemenr, LO 7915r. 18) Sa elemenr, LO 7916r. 19) Sdl elemenr, LO 7917r. 20) Se elemenr, LO 7918r. 21) Sd2 elemenr, LO 7919r. A. LOFGREN, SEPTIMEMBRATE CORNUODUS P!. l 180 A.LOFGREN

The relationship between Cornuodus and other 1981 Cornuodus longibasis (Lindstriim)- AN, pl. 2, figs. 24, genera has been discussed by several authors: Bergstrom 25. 1981 Cornuodus longibasis (Lindsrriim, 1955a) - LINDSTROM, (1981), in the Treatise, referred Cornuodus to "Famiiy p. 89, Cornuodus-Plate l, figs. 2-4. Unknown"; Stouge (1984) fìrst combined Cornuodus 1981 Cornuodus bergstroemi Serpagli, 1967 - LI NDSTROM, p. with, for instance, Scafpellodus, Walliserodus and 93, Cornuodus-Plate l, figs. 5-7. Belodella as the Family Cornuodontidae; Dzik (1991) 1983 Cornuodus longibasis (Lindstriim)- AN et al., p!. 8, figs. referred Cornuodus, Dapsilodus, Scabbardella, 6-7 (non figs. 1-5). 1984 Cornuodus longibasis (Lindstriim) - STOUGE, p. 62, pl. Decoriconus, Besselodus and Strachanognathus to the 8, figs. 1-8. Famiiy Strachanognathidae Bergstrom, 1981, regarding 1985 Cornuodus longibasis (Lindstriim)- AN et al., pl. 10, the name as synonymous with Cornuodontidae Stouge, figs. 9-12. I wouid much prefer t? piace .Cornuodus in the 1987 Cornuodus longibasis (Lindstriim) - NI & LI, pl. 55, fig. 9. Famdy Protopanderodonttdae Lmdstr6m, 1970 1988 Cornuodus longibasis (Lindsrriim)- STOUGE & BAGNO LI, together with Protopanderodus and Drepanodus, etc. (see p. 114, pl. l, figs. 20-21. Generai characteristics). 1988 Cornuodus longibasis (Lindstriim, 1955)- BERGSTROM, p. 225, pl. l, fig. 3. 1989 Cornuodus longibasis (Lindstriim) - CHEN & ZHANG, Tab. 2, pl. 2, figs. 8-10. CORNUODUS LONGIBASIS (Lindstrom, 1955) 1990 Cornuodus longibasis (Lindsrriim) - STOUGE & BAGNOLI, Pls. l, 2, 3 p. 14, pl. 3, figs. 3-7. 1990 Cornuodus longibasis (Lindstriim) - AN & ZHENG, pl. 1955 Drepanodus longibasis n. sp. - LI NDSTROM, p. 564, pl. 4, figs. 11, 12. 3, fig. 31. 1991 Cornuodus longibasis (Lindstriim, 1955)- D ziK, fig. 5A. 1966 Cornuodus erectus n. sp. - FAHRAEUS, p. 20, pl. 2, fig. 1991 Cornuodus bergstroemi Serpagli, 1967 - D ZIK, fig. 5B. Sa, b; text-fig. 2B. 1991 Cornuodus longibasis (Lindstriim)- N1 et al., p!. l, figs. 1967 Cornuodus bergstroemi n. sp.- SERPAGLI, p. 57, pl. 12, 9, 10. figs la-2c. non 1993 Cornuodus longibasis (Lindstriim, 1955) - LEHNERT, pl. 1967 Cornuodus erectus Fahraeus- SERPAGLI, p. 57, pl. 12, l , figs. 7-8. figs. 5a-8c. 1994 Cornuodus longibasis (Lindstriim, 1955) -DziK, p. 61, 1967 Cornuodus montanaroe n. sp. - SERPAGLI, p. 58, pl. 12, p!. 11, figs. 8-13, texr-fig. 4a. figs. 3a-4b. 1994 Cornuodus bergstroemi Serpagli, 1967 - D ZIK, p. 62, p!. 1967 Drepanodus sp. - SERPAGLI, p. 68, pl. 15, fig. 6a-c. 11, figs. 14-19, texr-fig. 4b. 1967 Scandodus? lanzaensis n. sp. - SERPAGLI, p. 95, pl. 26, 1995 Cornuodus longibasis (Lindstriim 1955)- LEHNERT, p. figs. 4a-7d. 80. 1970 Cornuodus erectus Fahraeus- LEE, p. 315, pl. 7, fig. 9. 1995 Cornuodus longibasis (Lindstriim)- ALBANESI et al., pl. 1974 "Cornuodus" longibasis (Lindsrriim)- SERPAGLI, p. 27, 3, fig. 9. pl. 7, fig. 2, pl. 20, fig. 12. 1995 Cornuodus longibasis (Lindsrriim, 1955) - WANG & 1974 Protopanderodus longibasis (Lindstriim) - VAN W AMEL, BERGSTROM, pl. 7, fig. 2. p. 92, pl. 4, figs. 4-6. 1995 Cornuodus longibasis (Lindstriim)- LOFGREN , Fig. 9an- 1976 Scalpellodus (?Cornuodus) laevis sp. n .- D ZIK, p. 421, ar. pl. 41, fig. l. 1996 Cornuodus longibasis (Lindstriim)- LOFGREN, Fig. 5AE. 1976 Cornuodus longibasis (Lindstriim) - LANoiNG, p. 631 , 1997 Cornuodus longibasis (Lindsrriim) - ARMsTRONG, p. 785 pl. l, figs. 12, 13, 15. (pars), pl. 4, figs . 13-20, non fig. 12, ?figs. 21-22. 1978 Cornuoaus longibasis (Lindstriim) - LOFGREN, p. 49, p!. 1992 Drepanoistodus suberectus (Branson & Mehl) - 4, figs. 36, 38-42, rexr-fig. 25A-C. ARMSTRONG, pJ. l , figs. 12, 13 (only). 1978 Cornuodus bergstroemi Serpagli- LOFGREN, p. 51, p!. 4, 1997 Scandodus? lanzaensis Serpagli- BERGSTROM et al., fig. fig. 37, texr-fig. 25D. 7H. 1981 Cornuodus longibasis (Lindsrriim) - CooPER, p. 161 , 1998 Cornuodus longibasis (Lindstriim) - ZHANG, p. 57, pl. p!. 26, figs. l 0-11. l, figs. 15-19.

EXPLANATION OF PLATE 2

Figs. 1-13 - Cornuodus longibasis (Lindstriim, 1955) from sample HK88-2, E.? variabilis- M. parva Subzone (=Lenodus variabilis Zone of Zhang, 1998), Hiillekis quarry, Vastergiitland. l) Pa element, inner side, LO 7920t, x140. 2) Pa element, inner side, LO 792lt, xl40. 3) Pb element, inner side, LO 7922t, xl lO. 4) Se element, LO 7923t, xl40. 5) Sa element, LO 7924t, x110. 6) Sb juvenile element, inner side, LO 7925r, xl40. 7) Pb element, outer side, LO 7926t, x140. 8) Sb element, inner side, LO 7927t, xl lO. 9) Sa element with additional posterior srriae, LO 7928r, x140. lO) Sd2 element, inner side, LO 7929t, xl40. 11) Sdl element, outer side, LO 7930t, xl40. 12) Sdl elemenr, inner side, LO 793lt, xl40. 13) Sd2 element, almost complete, ourer side, LO 7932t, x140. A. LOFGREN, SEPTIMEMBRATE CORNUODUS P!. 2 182 A.LOFGREN

1998 Cornuodus sp. A- ZHANG, p. 58, p!. 2, figs. 16-20. imo the base-cusp bend (Pl. l, figs. l, 8, 15). Strati- 1998 Cornuodus longibasis (Lindstrom, 1955)- ALBANESI, p. graphically o l der specimens are generally more strongly 118, pl. 2, figs. 30-33. 1998 Cornuodus bergstroemi Serpagli, 1967 -ALBANESI, p. recurved (Pl. 3, fig. 4) than younger representatives 118, p!. 2, figs. 26-29. (Pl. l, fig. 15, Pl. 2, fig. l) with some exceptions (cf. Pl. 3, fig. lO, an almost erect element from the O. evae Zone) and are also slighdy less symmetrical, the basai Emended diagnosis - A species of Cornuodus cavity opening to the inner side. There is no consistent consisting of recurved Pa elements with a comparatively variation stratigraphically in the development of the short base and antero-basal quasi-hook; erect Pb quasi-hook. Ontogenetically it seems to be most elements with a slightly longer base and the anterior evident in young adults. edge extending from just below the base-cusp bend upwards; erect to prodined symmetrical Sa and slightly Pb element - Cusp erect to slighdy redined and asymmetrical Sb elements with a long, narrow base; strongly compressed laterally with sharp anterior and erect to redined Se elements with a sharp base-cusp posterior edges (Pl. 3, fig. 11). The anterior edge arises bend an d usually erect Sd elements with a long, narrow halfWay up the base, i.e. below the transition between twisted base, shorter an d wider in Sd l than in Sd2 the base and cusp. In some specimens there is a costa elements. Ali element types have a laterally compressed or carina o n each side of the cusp dose to the posterior cusp, a long cylindrical base with a thin basai cavity edge (Pl. 2, fig. 3); others have a rounded centrallateral wall, and microornamentation consisting of faint carina on each side of the cusp (Pl. 2, fig. 7). Base striae restricted to the posterior cusp relatively short and only very slightly compressed margm. laterally. Basai cavity conica! with an extended tip (Pl. l, fig. 16). Stratigraphically younger specimens are only Element descriptions slighdy asymmetrical, while older specimens are more dearly concavo-convex with the base flaring to the inner Pa element- Cusp recurved, strongly compressed side, the posterior edge of the cusp displaced to the laterally, with anterior and posterior edges; posterior outer side and the anterior edge to the inner side (Pl. edge with a costa or strong carina on each side dose to 3:, fig. 11). this edge (Pl. 2, fig. 1). Rarely, the inner side is almost flat (Pl. l, fig. 15, Pl. 2, fig. 2). Base short, slighdy Sa element- Cusp almost erect, larerally compressed compressed laterally. Oral margin short, unkeeled, with sharp anterior and posterior edges (Pl. 2, fig. 5) straight or slightly concave in latera! view. Anterio-basal and a costa dose to the posterior edge o n each side (P l. corner characteristically bent upwards (Pl. 3, figs. 4, 3, fig. 8), the edge arising on the oral margin, often l O). This "quasi-hook" development is often more near the base-cusp bend. In some specimens there are evident when the element is seen from the outer side, also minor additional posterior costae (Pl. 2, fig. 9). than from the inner side. Basai cavity extending up The cusp is only slighdy longer than the base. The base

EXPLANATION OF PLATE 3

Figs. 1-7 - Cornuodus longibasis (Lindstrom, 1955) 1-7 - "Normal" popularion from Baltoniodus navis Zone, Oland. l) Sa elemem from sample 0194-1, top of middle B. navis Zone, Sandvik, LO 7933r, xl lO. 2) Se element from sample 0195-2, top of B. navis Zone, Gillberga quarry, LO 7934t, xl lO . 3) Sb elemem, ourer side, sample 0195-2, top of B. navis Zone, Gillberga quarry, LO 7935r, xl lO. 4) Pa element from sample 0195-2, top o.f B. navis Zone, Gillberga quarry, LO 7936t, x140. 5) Sdl element, inner side, from sample 0195-2, top of B. navis Zone, Gillberga quarry, LO 7937r, xl lO. 6) Sd2 elemem, ourer side, from sample Ql95-3, top of middle B. navis Zone, Gillberga quarry, LO 7938r, xlOO. 7) Sdl element, outer side, from sample 0195-3, top of middle B. navis Zone, Gillberga quarry, LO 7939r, xl lO. 8-13 - "Normal" population from sample Vg89-B4, upper middle Oepikodus evae Zone, Orreholmen quarry, Vasrergiirland. 8) Sa element, LO 7940t, x140. 9) Sb element, rather shorr-based, LO 794lt, x140. lO) Pa element, LO 7942r, x140. 11) Pb element, inner side, LO 7943t, xl lO. 12) Se element, rarher long-based, LO 7944t, x140. 13) Sd2 element, inner side, LO 7945t, x140. 14-20 - Long-based popularion from sample Na 87-5, middle B. navis Zone, Gymninge, Narke. 14) Pa element with slighrly damaged base, LO 7946r, x140. 15) Pb? element, LO 7947t, xl 50. 16) Sa element, LO 7948r, xl lO. 17) Sb element, LO 7949r, x140. 18) Sd2 element, LO 7950r, xl 50. 19) Sdl elemem, ourer side, LO 7951 t, x140. 20) Se elemem, LO 7952r, xl 50. A. LDFGREN, SEPTIMEMBRATE CORNUODUS Pl. 3 184 A.LOFGREN is not laterally flattened, being rounded in cross- Carni c Al p elements most closely resemble some early section (Pl. 3, fig. 1). The basai cavity is deep and middle Arenig (Early Ordovician) specimens from conical with a thin, drawn-out apex, extending to or Sweden (P l. l, figs. 8-14). Both these faunas are just above the base-cusp bend (Pl. l, figs. 10, 18). characterized by the particularly long base in several element types, particularly Pb and Sd2 elements (cf. Sb element - Cusp erect, slightly longer than the Pl. l, figs. 3, 7, 9, 14). The characteristically recurved base, laterally compressed and with keeled edges (Pl. Pa element is aiso similar in these two faunas (P l. l, 2, fig. 8). Posterior edge slightly bent outwards. Thin figs. l, 8). In the majority of my Swedish C. longibasis costae may occur posteriorly at the base-cusp bend (P l. collections (see Pl. l, figs. 15-21) the base is relatively 3, fig. 3). Base widened aborally, flaring somewhat to shorter, particularly in Pb, Se and Sdl elements. In the inner side (Pl. 2, fig. 6); irregularly oval in cross- Sweden there is no consistent morphologicai trend from section. The whole element is slightly asymmetricai, the Tremadoc and early Arenig faunas to the Llanvirn which distinguishes it from the Sa element. faunas. The aberrant early middle Arenig population in centrai Sweden, which most dosely resembles the Se element- Cusp erect (Pl. 3, fig. 12) to redined Ashgill population from the Carni c Alps, thus does no t (P l. 3, fig. 2), strongly compressed lateraily with sharp represent a separate species, in my opinion, but rather edges and with a lateral costa on each side dose to the comprises an ecomorphotypic variant of typical C. posterior edge (Pl. 3, fig. 20) rarely with additional longibasis. minor costae dose to this. The base is shorter than in A further ecomorphotype is possibly represented the other S elements, laterally compressed, but fairly by a population from the Middle Ordovician of the broad (P l. 2, fig. 4). Basai cavity ending in an extended Southern Uplands of Scotland (Armstrong, 1997). tip at the base-cusp transition (Pl. l, fig. 20). The Alternatively, these elements with a CAI of 5 could element is aimost symmetricai. have become slightly deformed (as can be seen in some other of the specimens illustrateci). The suberect Sdl element- Cusp erect (Pl. l, fig. 12) to recuived symmetrical element attributed to this apparatus (Pl. 3, fig. 7), laterally compressed, with fairly sharp (Armstrong, 1997, pl. 4, fig. 12) probably instead edges. The anterior edge is slightly displaced to the inner belongs to Drepanoistodus suberectus from the same side and the posterior edge directed outwards (Pl. 3, sample. The "symmetrical" element that Armstrong fig. 5), sometimes with faint additional costae. Base assigned to D. suberectus seems to me to be the Pa fairly long, flaring strongly to the inner side (P l. 2, fig. element of C. longibasis. 12) and irregularly rounded in cross-section (Pl. l, figs. Zhang (1998) described Cornuodus sp. A from the 12, 19). Basai cavity fairly deep, extending to the base- Middle Ordovician of south-centrai China as a taxon junction (Pl. l, fig. 12). The element in its entirety where elements had wider cusps than is usuai in C. IS concavo-convex. longibasis. This may be another instance of ecophenotypic variati o n within C. longibasis, but should Sd2 element- Cusp erect (P l. 3, fig. 6) to slightly the Pa element illustrateci (Zhang, 1998, pl. 2, fig. 20) proclined (Pl. 2, fig. 13), with rounded sides but fairly really belong to Cornuodus, I agree with Zhang (1998) sharp anterior and posterior edges which are slightly that. it (and associateci elements) belong to a new displaced, the posterior edge to the outer side (Pl. 2, speCies. fig. 13) and the anterior edge to the inner side (Pl. 2, fig. lO). The base is longer than in the other elements Materia/- 852 Pa, 959 Pb, 696 Sa, 1969 Sb, 1276 and rather narrow (Pl. l, fig. 14). Basai cavity deep Se, 1435 Sdl, and 770 Sd2 elements; 7,957 specimens (P l. l, fig. 2 I), narrow dose to the cusp, then fairly in ail (including 379 specimens from populations with abruptly widening downwards about haifway to the particularly long-based morphotypes). aboral margin (Pl. 2, fig. lO). The element is concavo- convex but somewhat less so than the Sdl element and Stratigraphic distribution - From the Tremadoc is slightly twisted. Paltodus deltifer Zone in t o the Ashgill ordovicicus Zone. Remarks - The holotype of Drepanodus longibasis Lindstrom, 1955 is an incompletely developed Sa element from the lower Arenig, while the holotype of ACKNOWLEDGEMENTS Cornuodus erectus Fahraeus, 1966 is an Sb element and Grants to the projects "Early Ordovician biostratigraphy" and its co-type a Pb element, both from the Llanvirn. As "Early Ordovician conodonts in Sweden" from the Swedish Natural indicated in P l. l, figs. 1-7, the Ashgill fauna of Science Research Council (NFR) financed laborarory treatment Cornuodus described an d illustrateci by Serpagli ( 1967) of many of the samples and most of the SEM work. Professar Maurits Lindstri:im, Srockholm, critically read the manuscript and probably includes ail element types that can aiso be he and an anonymous referee contributed useful comments. A found in my stratigraphically older C. longibasis number of students at the Department of Geology in Lund have collections. In some respects Serpagli's Late Ordovician helped me pick out conodonts from the samples through the years. SEPTIMEMBRATE CORNUODUS 185

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