Sexual Phenomena in Late Jurassic Aspidoceratidae (Ammonoidea)

Home , Aspidoceras, Aspidoceratidae, Aspidoceratinae, Ataxioceras, Gravesia (ammonite)

Palaeodiversity 1: 181–187; Stuttgart, 30.12.2008. 181

Sexual phenomena in Late Jurassic Aspidoceratidae (Ammonoidea). Dimorphic correspondence between Physodoceras hermanni (Be r c k h e m e r ) and Sutneria subeumela Sc h n e i d , and first record of possible hermaphroditism

Ho r a c i o Pa r e n t , Ar m i n Sc h e r z i n g e r & Gü n t e r Sc h w e i g e r t

Abstract New collections of the dimorphic ammonite species Physodoceras hermanni (Be r c k h e m e r ) [M] and Sutneria subeumela Sc h n e i d [m] from the Upper Jurassic (Beckeri Zone, Subeumela Subzone, subsidens horizon) of Swabia demonstrates first time evidence of intra-sexual polyphenism in Aspidoceratidae. In the macroconchs two size classes demonstrate different times of maturity, leading to small and large adults. In the microconchs, besides a continuous size range of adults, a unique case of possible sexual change in a subadult stage is observed that could point to the occurrence of hermaphroditism in ammonites. K e y w o r d s : Ammonitina, Physodoceratinae, ontogeny, sexual dimorphism, polyphenism, Late Jurassic.

Zusammenfassung Neue Aufsammlungen der dimorphen Ammoniten Physodoceras hermanni (Be r c k h e m e r ) [M] und Sutneria subeumela Sc h n e i d [m] aus dem Oberjura (Beckeri-Zone, Subeumela-Subzone, subsidens-Horizont) der Schwäbi schen Alb erbringen den Erstnachweis von innerartlichem Polyphenismus der Aspidoceratidae. Bei den Makro- conchen lassen sich zwei Größenklassen unterscheiden, die unterschiedlichen Beginn der Geschlechtsreife anzei- gen. Dies führt zu kleinen Individuen und großen Individuen. Bei den Mikroconchen ist eine kontinuierliche Variationsbreite festzustellen. Daneben wurde ein möglicher Fall von Geschlechtsumwandlung im subadulten Sta- dium gefunden, was auf das Vorkommen von Zwittrigkeit bei Ammoniten deuten könnte.

Resúmen Colecciones recientes del par dimórfico conformado por Physodoceras hermanni (Be r c k h e m e r ) [M] y Sutneria subeumela Sc h n e i d [m] del horizonte subsidens, Subzona Subeumela, Zona Beckeri (Jurásico Superior) obtenidas en Swabia demuestran por primera vez evidencia de polifenismo intra-sexual en la familia Aspidoceratidae. En las macroconchas la existencia de dos clases de talla adulta demuestra diferentes momentos de maduración sexual. Esta estrategia reproductiva origina adultos pequeños por maduración sexual precoz y adultos de mayor talla. En las microconchas, con variación contínua de talla adulta, un caso notable de posible cambio de sexo en un estado subadulto es observado, lo cual podría interpretarse como un caso de hermafroditismo en amonites.

Contents 1. Introduction ...... 181 2. Antecedents and new material...... 183 3. Discussion and conclusion...... 186 4. References ...... 186

1. Introduction Qu e n s t e d t , 1849) and the microconch species of Sutneria Zi t t e l , 1884 (type species: Nautilus platynotus Re i n e c k e , The strongest argument for sexual dimorphism in am- 1818) has been suggested (En a y 1977: 109; Sc h w e i g e r t monoids is the identity of juvenile ontogenies between 1997). The systematic position of Sutneria was long a case pairs of contemporaneous ammonites which attain differ- of controversial debate, and for a long time it was tenta- ential adult sizes and characteristic morphologies (e. g., tively included in Aulacostephaninae (Ze i ss 1979; Ol ó r i z Ma k o w s k i 1962; Ca l l o m o n 1963; recent review in Da v i e s & Ro d r í g u e z -To v a r 1996). Recently, Sc h w e i g e r t (1998) et al. 1996); the larger dimorph or macroconch should be has demonstrated that Sutneria belongs to the family As- the female and the smaller or microconch the male. Di- pidoceratidae by the possession of a laevaptychus. Never- morphic correspondence between the macroconch species theless, it seems that there are no published studies on of Physodoceras Hy a t t , 1900 (type species: Ammonites correspondence between species in particular. Sutneria circumspinosus Opp e l , 1863 = Ammonites circumspinosus and Physodoceras are geographically wide-spread, espe- 182 p a l a e o d i v e r s i t y 1, 2008

Fig. 1. Map showing the locality (asterisk) of provenance of the studied ammonites.

cially in peri-Tethyan basins and shelves, the western Tethyan Realm itself, and migrated even into the Subbo- real, Andean and Indo-Madagascan provinces (e. g. St e u - e r 1897; Ge y e r 1969; Ze i ss 1979). Physodoceras hermanni [M] (Be r c k h e m e r , 1922) and Sutneria subeumela [m] Sc h n e i d , 1915 frequently occur associated to each other (often even in the same piece of rock) in the Subeumela Subzone (Beckeri Zone, Late Kim- Fig. 2. Chronostratigraphic age and range of Physodoceras her manni (Be r c k h e m e r ) and Sutneria subeumela Sc h n e i d . Chro- meridgian) of Southern Germany (Sc h n e i d 1915; Be r c k - nostratigraphy after Sc h w e i g e r t (2007). (1): Type horizon of h e m e r 1922; Ro l l 1931; Be r c k h e m e r & Hö l d e r 1959). P. hermanni and most probably of S. subeumela. The Pseudo- Both taxa have been also recorded outside their type areas, mutabilis Zone is not yet studied in detail. from Le Pouzin in SE France (Hö l d e r & Zi e g l e r 1959), and from Bulgaria (Sa p u n o v 1977). Sutneria subeumela was also recorded in the Volgian Gorodishche section of e y e r c h e r z i n g e r i t t a Central Russia (G 1969; S & M 2006), 1925. Sc h i n d e w o l f (1925), on the one hand, did not recog- and a very close specimen was described from Ethiopia nize the relationship between Enosphinctes and Sutneria, (Ze i ss 1979). Therefore, the microconch Sutneria subeu but interestingly included Sutneria in the same family as mela is considered as a very good example of a geographi- Physodoceras. After consideration of the close relation- cally widespread guide-fossil. The macroconchs are much ship between Sutneria eumela and Sutneria subeumela less significant and often show homoeomorphism, per- several authors assigned both species to Sutneria (e. g. haps following a pattern of slower or less conspicuous Be r c k h e m e r & Hö l d e r 1959; Hö l d e r & Zi e g l e r 1959; morphologic evolution. En a y 1977; this paper). Also Ba r t h e l (1959) argued that In Southern Germany (Fig. 1) both taxa occur in the Enosphinctes and Sutneria are synonymous, whereas kiderleni, subsidens and fischeri horizons of the Subeu- Ge y e r (1969) considered Enosphinctes as a subgenus of mela Subzone (Fig. 2). En a y (1977: 109) was the first who Sutneria s. str. and pointed out that only the type species suggested they conform a sexual dimorphic pair based in of Enosphinctes, Sutneria subeumela, is characterized by the fact that they are the only species of Physodoceras and a ventral furrow. the only Sutneria with a well-defined ventral furrow. Ar k e l l (1957: L327) proposed the ventral furrow could be Acronyms of institutions due to the lost of the sipho, according to an idea of Sc h n e i d BSPM Bayerische Staatssammlung für Paläontologie und (1915: 124), but this was later definitely dismissed by Geologie, München, Germany SMNS Staatliches Museum für Naturkunde Stuttgart, Ger- Be r c k h e m e r & Hö l d e r (1959: 61–62) and Hö l d e r & many Zi e g l e r (1959: 194). The ventral furrow in S. subeumela LPB Laboratorio de Paleontología, Universidad Nacional led to a generic separation of Enosphinctes Sc h i n d e w o l f , de Rosario, Argentina p a r e n t e t a l ., s e x u a l p h e n o m e n a i n j u r a ss i c a sp idoceratidae 183

Acknowledgements Prof. Dr. Jo h n H. Ca l l o m o n (London) is cordially thanked for numerous fruitful discussions and comments on ammonites and dimorphism. Dr. Ma r t i n No s e (Munich) kindly loaned the type specimens of Sutneria subeumela for study. Dr. Ma r t i n Rö p e r (Solnhofen) communicated data on the locality of Brunn in Eastern Bavaria. Dr. Ma r í a E. Ré (Puerto Madryn) kindly provided recent specific literature. Prof. Dr. Pi e r r e Ha n t z p e r - g u e (Lyon) and an anonymous reviewer gave valuable sugges- tions as reviewers of the journal.

2. Antecedents and new material

Be r c k h e m e r (1922) based the definition of Physo doceras hermanni on ten specimens (currently stored in the SMNS, but only partly identifiable as being part of the syntypes series) coming from various localities in the Up- per Jurassic of Swabia (Fig. 1) but he did not designate any of these specimens as the type. The specimen from Gra- benstetten illustrated by Be r c k h e m e r (1922, pl. 1, fig. 12), erroneously said to be the “holotype” (Ch e c a 1985: 130), is here designated as the lectotype and refigured photographically (Fig. 3A3–A4). This specimen was slightly damaged by fire during Second World War; an older plas- ter cast of the specimen in original dimensions is still available (Fig. 3A1–A2). The type horizon of P. hermanni is the subsidens horizon of the Subeumela Subzone (Fig. 2). Ch e c a (1985) included Aspidoceras hermanni Be r c k h e Fig. 3. A. Physodoceras hermanni (Be r c k h e m e r ) [M], lectotype; subsidens horizon, Subeumela Subzone, Beckeri Zone, m e r in Pseudowaagenia Sp a t h , 1931 (type species: Am Late Kimmeridgian; Kaltental near Grabenstetten, near Bad monites haynaldi He r b i c h , 1868), because of the presence Urach, SW Germany. – A1–A2. Plastercast (SMNS 60042/2) of of an outer row of spines. This outer row of spines, how- the damaged original specimen (A3–A4: SMNS 60042/1). A1, A3. ever, is also present in other species of Physodoceras (e. g., Lateral views. A2, A4. Ventral views. B–C. Sutneria subeumela Sc h n e i d [m]; subsidens horizon, Sub- Sc h w e i g e r t 1998), but not developed or irregularly ar- eumela Subzone, Beckeri Zone, Late Kimmeridgian; Galgen- ranged in the innermost whorls, in contrast to the strongly berg near Wellheim, S Germany. – B. Lectotype (BSPM 1913 IX bituberculate ornamentation of inner whorls in Aspido 183). B1. Ventral view. B2. Lateral view. C. Syntype (BSPM 1913 ceras s. str. We consider the genus Pseudowaagenia Sp a t h , IX 183a). C1. Ventral view. C2. Semilateral view. – All natural size. 1931 to represent a junior synonym of Physodoceras Hy- a t t , 1900, although several taxa with a remarkably evolute whorl expansion included by Ch e c a (1985) in that genus (e. g. Aspidoceras acanthomphalus Zi t t e l ) may represent lustrated the suture line of this specimen (see Fig. 3C). The another lineage giving rise to Hybonoticeras. lectotype and topotype of S. subeumela were collected Sc h n e i d (1915) based the definition of Sutneria subeu from an unspecified horizon, but according to co-occur- mela on three specimens: the one figured in the pl. 6, fig. ring oppeliids illustrated by Sc h n e i d (1915) it is very likely 7 of his paper coming from the vicinity of the village that it comes from the subsidens horizon (see Fig. 2). Wellheim in Franconia, a second one from the same local- Present authors have collected abundant ammonites ity and bed, and a further specimen from Nusplingen in from the type horizon of both species (subsidens horizon, Swabia, published as Ammonites n. sp. by Ha i z m a n n Subeumela Subzone) at Grabenstetten near Bad Urach, (1902, pl. 14, fig. 5). The specimen originally figured by Swabia and other localities nearby, including several spec- Sc h n e i d (1915, pl. 6, fig. 7) was refigured photographically imens of P. hermanni and S. subeumela. by Schlegelmilch (1994, pl. 59, fig. 12) erroneously as the Surprisingly, one of these newly collected specimens “holotype”, following Ba r t h e l (1959) and Ze i ss (1979). of S. subeumela is exceptionally well-preserved, showing, This specimen (Fig. 3B) is herein formally designated as after dissection, its inner whorls identical, at comparable the lectotype. The other specimen from Wellheim, now diameter, with those of P. hermanni collected in the same representing not only a syntype but also a topotype, was horizon (Fig. 4). The last whorl of the phragmocone of this mentioned as the “paratype” by Ba r t h e l (1959) who il- well preserved microconch specimen is moderately evo- 184 p a l a e o d i v e r s i t y 1, 2008

Fig. 4. Sutneria subeumela Sc h n e i d [m]; subsidens horizon, Subeumela Subzone, Beckeri Zone, Late Kimmeridgian; Gra- benstetten near Bad Urach, SW Germany. Adult specimen (SMNS 67288/1; leg. A. Sc h e r z i n g e r ) showing the phragmocone with the exact morphology of the macroconch, passing in the body-chamber to the typical morphology of the microconch.

– A1–A2: Natural size; A3–A4: Double size.

Fig. 5. Physodoceras hermanni (Be r c k h e m e r ) [M] / Sutneria lute with compressed subelliptical whorl section, slightly subeumela Sc h n e i d [m], subsidens horizon, Subeumela Sub- higher than wide. The flanks are gently convex and the zone, Beckeri Zone, Late Kimmeridgian. – A–E: Möck quarry venter rounded. There are two rows of tubercles, one of at Grabenstetten near Bad Urach, SW Germany (leg. H. Pa r e n t ). them on the umbilical shoulder and the remaining on mid- A. Small adult macroconch (LPB 1071/1). A1. Left lateral view. A . Right lateral view. B. Complete adult microconch (LPB flank. There is a single primary rib connecting an umbili- 2 1071/2). B1. Ventral view. B2. Lateral view. B3. Detail of lappet, cal tubercle with a lateral tubercle. The rib is confined double size. C. Adult microconch (LPB 1077), lateral view. between the tubercles; the upper flank and venter are com- D. Complete adult microconch (LPB 1075). D1. Lateral view. pletely smooth. The whorl section of the body-chamber is D2. Ventral view. E. Inner whorls of an inflated microconch (LPB 1076). E . Lateral view. E . Ventral view. Double size. higher than wide, covered by densely spaced, strong fal- 1 2 F. Complete adult microconch (SMNS 67289; leg. G. Sc h w e i coid ribs; most of them bifurcate on mid flank given rise g e r t ); vicinity of Lenningen-Schopfloch, SW Germany. F1, F3. to a weak tubercle. Lateral views. F2, F4. Ventral views. F1, F2: Double size. G. Com- S. subeumela usually shows a wide range of morpho- plete adult microconch (SMNS 67288/2; leg. A. Sc h e r z i n g e r ); logical variation in adult size. However, within the studied Grabenstetten near Bad Urach, SW Germany. – Asterisk at last septum. All natural size, otherwise indicated. material the evolute specimen with bituberculated inner whorls described above is unique. Other specimens exhibit a typical morphology of the inner whorls, smooth with a row of periumbilical lamelliform tubercules (much Be r c k h e m e r 1922: 76) and the much larger specimens like in the innermost whorls of Physodoceras in general at (Fig. 7F) with adult diameters at the body-chamber which about 5 < D < 10 mm), but never bituberculate (cf. Figs. may be of 120 mm or more (previously determined as e r c k h e m e r ö l d e r 3C2, 5B–5F). ‘Aspidoceras longispinum’, e. g. B & H P. hermanni is represented by a wide variety of mor- 1959). Inner whorls of all the macroconchs show the ven- photypes in two classes of adult size and ornamentation. tral furrow which is characteristic of the species (inner The smaller specimens (Figs. 3A lectotype, 6A–B, 6D–E, whorls of a large macroconch are shown in Fig. 6C). Like 7A–7E) with a diameter ranging within 25–55 mm (see in S. subeumela the ventral furrow is only well visible in p a r e n t e t a l ., s e x u a l p h e n o m e n a i n j u r a ss i c a sp idoceratidae 185

Fig. 7. Physodoceras hermanni (Be r c k h e r m e r ) [M]; subsidens horizon, Subeumela Subzone, Beckeri Zone, Late Kimmeridg- ian; Grabenstetten near Bad Urach, SW Germany. – A–E. Mac- roconchs of the small morphotype with nearly complete body- chamber (SMNS 67292, five specimens; leg. A. Sc h e r z i n g e r ). A. Ventral view showing the ventral furrow. F. Adult macro- Fig. 6. Physodoceras hermanni (Be r c k h e m e r ) [M]. – A. Syn- conch of the large morph, almost complete (SMNS 67293; leg. c h w e i g e r t type (SMNS 60042/3; He r m a n n collection); subsidens horizon, G. S ); Lenningen-Schopfloch, near Grabenstetten. – Subeumela Subzone, Beckeri Zone, Late Kimmeridgian; Kal A–E: Natural size, F: × 0.6. tental near Grabenstetten, near Bad Urach, SW Germany. B–D. Three specimens (SMNS 67291/1–3; Br a c h e r collection) from subsidens horizon, Subeumela Subzone, Beckeri Zone, Late imens are shown in Figs. 3A, 5A, 6A–B, 6D–E and 7A– Kimmeridgian; Herrlingen-Lautern near Ulm, SW Germany. C. Ventral view of inner whorls of a large macroconch showing 7E. When comparing the macroconchs, the smaller ones the ventral furrow. E. Specimen (SMNS 67293; leg. G. Sc h w e i seem to have the ontogenetic development precociously g e r t ) from kiderleni horizon, Subeumela Subzone, Beckeri halted by early sexual maturation (progenesis) in respect Zone, Late Kimmeridgian; vicinity of Lenningen-Schopfloch, to the larger ones. SW Germany. – Asterisk at last septum. All natural size. In the sampled horizons, due to the very hard and pure limestone and the frequent presence of fragmented shells, it is impossible to collect their ammonite content in quan- few cases because when the steinkerns were laterally com- tity. This situation precludes accessory statistical analysis pressed during early diagenesis, the ventral furrow disap- of the described patterns of structure of the species. How- peared. Even in the lectotype the furrow is very weak. ever, after several years of sampling it became obvious Preservation of the furrow, however, is much better if the that the abundance of microconchs, small and large mac- specimens are vertically embedded. Then, if there is no roconchs markedly differs in various outcrops. In the cen- lateral compression, the furrow shows its original dimen- tral part of the Swabian Alb (e. g. vicinity of Graben- sion (Figs. 6C, 7A). The smaller adults have a rather weak stetten, Lenningen-Schopfloch), the small specimens of ornamentation which fades out on the body-chamber, but P. hermanni and the corresponding microconch S. subeu in the larger specimens the ornamentation continues al- mela are almost equally frequent, whereas the large mac- most to the end of the body-chamber. Representative spec- roconchs are rare, always less than 5% of the samples. 186 p a l a e o d i v e r s i t y 1, 2008

Another rather large sample comes from scientific excava- The unique microconchiate S. subeumela showing a tions in the laminated limestones of Brunn in Eastern Ba- bituberculate sculpture stage, undoubtedly typical for fe- varia (Rö p e r et al. 1996). There, S. subeumela and the males, suggests either a weak sex determination (her- large morph of P. hermanni are both extremely rare, maphroditism?) or a sex change in the subadult stage. This whereas the small P. hermanni – interpreted by Rö p e r et phenomenon is not unusual in gastropods (e. g., Calyptra al. (1996) as juveniles – is the most common ammonite of ea La m a r c k , 1799) and other mollusks, but there are only this locality, and the ratio between microconchs and small two recently described, rather inconclusive cases in ce- macroconchs is ca. 1 : 100. The small specimens of P. her phalopods: pseudohermaphroditism (Or t i z & Ré 2006), manni (‘Aspidoceras’ in Ke u pp et al. 1999) are often settled and sex change or intersexuality (Ho v i n g et al. 2006). with barnacles during life. The locality of Brunn is dated Ho v i n g et al. (2006) found within samples of Ancistro in the kiderleni horizon of the Subeumela Subzone cheirus lesueurii (d’Or b i g n y , 1842) some intersexual (Sc h w e i g e r t 2007). males (intermediate in size between normal males and fe- males) with nidamental glands, but they attributed the phenomenon to some external environmental factors not 3. Discussion and conclusion related with the natural environment of the species. In the fossil case it may be questioned if such phenomenon is In summary P. hermanni and S. subeumela are charac- unique or widespread but overlooked. Indeed at least one terized by a wide variety of morphotypes in a continuous other hot candidate for an intersexual microconch has series of intraspecific variation, and additionally by a co- been illustrated by Sy k e s & Ca l l o m o n (1979) in another occurring larger morphotype of Physodoceras. Therefore, family of Jurassic ammonites, in the genus Ringsteadia besides a sexual dimorphism between microconchs and Sa l f e l d , 1913. Usually the genus Ringsteadia is coupled macroconchs, a second macroconch morph occurs. This with the microconch genus Microbiplices Ar k e l l , 1936 observation points to different times of sexual maturation (see, e. g., Sc h a i r e r & Sc h l a m pp 2003). From the Oxford- of macroconchs within the populations. It is the question ian of Scotland, a specimen of Ringsteadia caledonica which of the two size classes of macroconchs is the normal Sy k e s & Ca l l o m o n , 1979 showing the subadult sculpture for the genus. Considering other dimorphic pairs in spe- of a macroconch unexpectedly developed a lappet and cies of Sutneria – Physodoceras, e. g. S. platynota (Re i thus obviously changed into a microconch (Sy k e s & Ca l - n e c k e , 1818) and P. circumspinosum (Qu e n s t e d t , 1849) l o m o n 1979, pl. 121, fig. 9). Moreover, some specimens the macroconchs are approximately 5 to 6 times larger described as Ataxioceras (Schneidia) by At r o ps (1982) than the corresponding microconchs. In contrast, the small exhibit an unusually narrow umbilicus strongly resem- P. hermanni morph is only one and a half to two times bling female, macroconch, individuals, but they develop larger than the microconch S. subeumela. [A quite similar lappets at their mouth borders. observation can be made in Sutneria casimiriana (Fo n - t a n n e s , 1879) and the co-occurring physodoceratids from 4. References the ornatum horizon of the Setatum Subzone of Swabia, but this is not outlined here]. 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Addresses of the authors: Ho r a c i o Pa r e n t , Laboratorio de Paleontología, Universidad Nacional de Rosario, Pellegrini 250, 2000 Rosario, Argentina E-mail: [email protected] Ar m i n Sc h e r z i n g e r , Hewenstr. 9, 78194 Immendingen-Hattingen, Germany E-mail: [email protected] Gü n t e r Sc h w e i g e r t , Staatliches Museum für Naturkunde, Rosenstein 1, 70191 Stuttgart, Germany E-mail: [email protected]

Manuscript received: 22.4.2008, accepted: 15.10.2008.