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Zeitschrift/Journal: Carolinea - Beiträge zur naturkundlichen Forschung in Südwestdeutschland

Jahr/Year: 2009

Band/Volume: 67

Autor(en)/Author(s): Giersch Samuel, Bernor Raymond L.

Artikel/Article: Anchitherium aurelianense (, Mammalia) from the Middle of the Bohlinger Schlucht, South-West Germany 13-18 ©Staatl. Mus. f. Naturkde Karlsruhe & Naturwiss. Ver. Karlsruhe e.V.; download unter www.zobodat.at

carolinea, 67 (2009): 13-18, 4 Abb.; Karlsruhe, 15.12.2009 13

Anchitherium aurelianense (Equidae, Mamma- lia) from the Middle Miocene of the Bohlinger Schlucht, South-West Germany

SAMUEL GIERSCH & RAYMOND L. BERNOR

Abstract gehörigkeit des Fundes zur Unterart A. aurelianense The Middle Miocene (Upper Badenian, MN6) local- hippoides und die Beziehung der Fundstelle zu gleich ity Bohlinger Schlucht (Hegau District, South-West alten Fundstellen in Westeuropa diskutiert. Germany) has yielded a diverse assemblage of land and lower vertebrates. After discovery in Authors 2003, the ongoing excavations increased the number SAMUEL GIERSCH, Staatliches Museum für Naturkunde, of taxa and here we report on the first equid remains of Referat für Paläontologie und Evolutionsforschung, Anchitherium aurelianense from the locality. The best Erbprinzenstraße 13, D-76133 Karlsruhe; taxonomic referral of this specimen is to the subspecies E-Mail: [email protected] A. aurelianense hippoides. A comparison of the Bohlin- RAYMOND L. BERNOR, College of Medicine, Department of ger Schlucht locality to contemporaneous Western Anatomy, Laboratory of Evolutionary Biology, Howard Europe localities is further discussed herein. University, 520 W. St. N.W., Washington D.C. 20059 E-mail: [email protected] and [email protected] Kurzfassung Anchitherium aurelianense (Equidae, Mammalia) aus dem Mittelmiozän der Bohlinger Schlucht, 1 Introduction Südwest-Deutschland Die mittelmiozäne (Ober-Badenium, MN6) Fundstelle The narrow and steep canyon of “Bohlinger Bohlinger Schlucht in Südwestdeutschland enthält eine Schlucht” is located on the Höri-peninsula near diverse Fauna von Landsäugetieren und niederen Wir- beltieren. Die Fundstelle wurde 2003 entdeckt. Fortge- the western margin of Lake Constance in South setzte Ausgrabungen erhöhten kontinuierlich die Arten- West Germany (topographic map 8219, Sin- 34 52 zahl. Mit dem Fund von Anchitherium aurelianense liegt gen (Hohentwiel), R 92156, H 85186; fig. 1). nun zum ersten Mal ein Nachweis für Pferde (Equidae) There we find exposed sediments of the Mid- aus der Fundstelle vor. Im Folgenden wird die evtl. Zu- dle Miocene Upper Freshwater Molasse. The

Figure 1. Location of Bohlinger Schlucht (asterisk) in the He- gau-district on the Höri-penin- sula near Lake Constance. ©Staatl. Mus. f. Naturkde Karlsruhe & Naturwiss. Ver. Karlsruhe e.V.; download unter www.zobodat.at

14 carolinea, 67 (2009) locality was first discovered in the middle of the Comparative material 19th century and has been recognized as being Original material from Sansan (MN6): NMB SS an important Miocene plant site (HEER 4877, 4878, 4879, housed in the Naturhistor- 1859, HANTKE 1954, RUTTE 1956). The “Schrotz- isches Museum in Basel (Switzerland). burg”-marls in the upper part of the Bohlinger Original material and casts from Steinheim Schlucht have yielded a diverse macro- and mi- (MN7): SMNS 43843 a, b, c, housed in the Mu- cro-flora, which was recently used for analysis seum für Naturkunde in Stuttgart. of palaeoclimate of the Middle Miocene (Upper- most Badenian-Lowermost Sarmatian) central Abbreviations Molasse basin (UHL et al. 2003, 2006). Addi- tionally, in 2003 vertebrate fossil bearing layers L Maximum length of the tooth crown were discovered by one of the authors (SG) in m1/2 lower first or second molar the Bohlinger Schlucht. The fossil bearing ho- m2 second lower molar rizons are within muscovite-rich, finegrained, m3 third lower molar loosely consolidated sands of the “Steinbalmen- SMNK Staatliches Museum für Naturkunde in sande”. Inside the Steinbalmensande occur the Karlsruhe “Krokodil-Schichten” in several horizons. These SMNS Staatliches Museum für Naturkunde in layers are channel-fillings consisting of re- Stuttgart worked, coarse-grained clays and marls which NMB Naturhistorisches Museum Basel contain bone fragments and teeth of mammals Wa Maximum width of anterior crescent of and reptiles as well as molluscs and plant re- tooth crown mains. More than 300 specimens of 22 differ- Wp Maximum width of posterior crescent of ent taxa and five reptile taxa including tooth crown the crocodylian Diplocynodon were discovered during first excavations in 2003. The mammal assemblage includes both micro- and macro- 3 Systematic Palaeontology mammal remains and is correlative with the upper part of mammal-Zone MN6, Upper Bad- Order Perissodactyla OWEN, 1848 enian (GIERSCH 2004 a, b). The occurrence of a Family Equidae GRAY, 1821 well dated fauna next to palaeoclimatologically Genus Anchitherium (CUVIER, 1812) significant plant-remains makes the Bohlinger Anchitherium aurelianense (CUVIER, 1812) Schlucht an extraordinarily important site for (Fig. 2, Tab. 1) palaeoecological studies of the Middle Miocene Type locality: Montabusard (France), Early in South West Germany. Ongoing excavations Miozene (MN4). unearthed further mammal taxa and the faunal list of 2006 contains the first equid remains of Locality: Bohlinger Schlucht near Bohlingen Anchitherium aurelianense, which we describe (Baden-Württemberg), Upper Freshwater Mo- herein. lasse, Steinbalmensande; Middle Miocene (Early Astaracian, MN6); 14,0-13,5 Ma.

2 Material and Methods Material: Specimen SMNK-PAL. 6600, Fragment of the left mandible with m2 and m3 in situ. The investigated material includes a fragment of the left mandible with m2 and m3. The specimen was prepared from its sandy matrix using hand tools and fixed with cyan acrylate glue. The spec- imen is housed in the palaeontological collection Table 1. SMNK-PAL. 6600 Achitherium aurelianense (CUVIER, 1812) from the Bohlinger Schlucht, Upper of the Staatliches Museum für Naturkunde in Freshwater Molasse (MN6), measurements in mm: Karlsruhe with the collection number SMNK-PAL. 6600. Position L Wa Wp For classification and terminology of dental struc- tures we follow ABUSCH-SIEWERT (1983) and DAXN- m2 inf. sin. 20.1 13.9 12.6 ER-HÖCK & BERNOR (2009). Digital photos were m3 inf. sin. 21.3 12.3 10.9 taken by the Authors. ©Staatl. Mus. f. Naturkde Karlsruhe & Naturwiss. Ver. Karlsruhe e.V.; download unter www.zobodat.at

GIERSCH & BERNOR: Anchitherium form the Bohlinger Schlucht, South-West Germany 15

Figure 2. Anchitherium aurelianense from Bohlin- ger Schlucht SMNK-PAL. 6600, left dentary with m2- m3 in A): lingual; B): oc- clusal and C): labial views. Scale: 10 mm. – Foto: S. GIERSCH. ©Staatl. Mus. f. Naturkde Karlsruhe & Naturwiss. Ver. Karlsruhe e.V.; download unter www.zobodat.at

16 carolinea, 67 (2009)

4 Description ectoflexid is closed labially by accessory enamel wrinkles. The crown exhibits a heavily worn dis- The fragment of the left mandible is broken me- tal aspect. The width of the posterior crescent is sial to m2. The root of the ramus mandibulae is smaller than the anterior crescent. preserved distal to m3. The insertion scar for tem- m3: The third molar resembles the general shape poromandibularis muscle is lost. The dentition is and proportions of m2; however, a prominent hy- brachydont with a crown height of approximately poconulid effects a lengthing of the crown distal- 50% of anterioposterior tooth length. ly. A deep hypoflexid separates the hypoconulid m2: The second molar is rectangular to trapezoi- from the hypoconid. An additional cuspid is lo- dal shaped in occlusal outline. A deep, labiolin- cated between the entoconid and hypoconulid on gually running ectoflexid divides the tooth crown the posterolingual edge of the crown. The labial into two crescent-shaped portions which are open cingulum is complete except for a brief abbrevia- lingually. The anterior crescent is formed by the tion on the hypoconid; the ectostylid is less pro- paralophid and protolophid. Metalophid and hy- nounced than in m2. The labial enamel walls of polophid form the posterior crescent. Metaconid, both teeth exhibit a fine, horizontally orientated metastylid and entoconid are prominent cusps striation. that protrude 2 mm above the occlusal plane. A small groove separates the metalophid from the metastylid. Ento- and metaflexid are posterolabi- 5 Discussion ally curved. The metaflexid is lingually closed by a slight lingual cingulid, which courses from the The medium sized brachydont equid Anchi- paraconid distally and comprises a small enamel therium first occured in Europe during the early cuspid anterolingual to the metaconid. A labial Miocene in the mammal-Zone MN3 (ABUSCH-SIE- cingulid nearly extends from the paraconid to the WERT 1983). In the middle Miocene Anchitherium entoconid, being interrupted only at the base of is abundant and the dominant equid within the the hypoconid. There is a prominent, albeit low mammal assemblages throughout Europe. Be- crowned ectostylid at the base of the crown. The tween 11.2 Ma and 10.6 Ma Anchitherium cooc-

Figure 3. Length to anterior width of m1/2 in different subspecies of A. aurelianense. Database after our own mea- surements and ABUSCH-SIEWERT (1983). The ellipses mark the 95% confidence interval. ©Staatl. Mus. f. Naturkde Karlsruhe & Naturwiss. Ver. Karlsruhe e.V.; download unter www.zobodat.at

GIERSCH & BERNOR: Anchitherium form the Bohlinger Schlucht, South-West Germany 17

Figure 4. Length to anterior width of m3 in different subspecies of A. aurelianense. Database after our own mea- surements and ABUSCH-SIEWERT (1983). The ellipses mark the 95% confidence interval.

curs in Europe with the larger and Therefore, the single specimen from Bohlinger and becomes abruptly extinct Schlucht is really insufficient to certainly refer this shortly after basal Late Miocene (BERNOR & AR- sample to the subspecies level. Nevertheless, a MOUR-CHELU 1999, DAXNER-HÖCK & BERNOR 2009, general trend can be recognized in SMNK-PAL. KAISER 2009). 6600: The measurements of m2 and m3 in An- ABUSCH-SIEWERT (1983) recognized three subspe- chitherium from the Bohlinger Schlucht (fig. 3 and cies-lineages in European Anchitherium aureli- 4) compare well with the middle of size-classes of anense. Based on morphological differences in Sansan A. a. hippoides (see also ABUSCH-SIEWERT dentitions, A. aurelianense aurelianense (CUVIER, 1983, p. 280, fig. 92; p. 281, fig. 93 and 94). Addi- 1812), A. aurelianense steinheimense ABUSCH- tional morphological characters visible in SMNK- SIEWERT, 1983 and A. aurelianense hippoides PAL. 6600 and typical for A. a. hippoides include (LARTET, 1851) were identified. Anchitherium a. the pronounced hypoconulid and complete labial aurelianenese ranged from Wintershof-West cingulid. A direct comparison with similar teeth (MN3) to Sandelzhausen and Georgensgmünd from Sansan housed in the NMB supports the (MN5). Anchitherium a. steinheimense is re- attribution of the Bohlinger Schlucht anchithere ported from Steinheim (MN7) and A. a. hippoides to Anchitherium a. hippoides. is recorded from Sansan (MN6) and La Grive The comparison of measurements of SMNK- (MN7) (DAXNER-HÖCK & BERNOR 2009). The evo- PAL. 6600 with the older A. a. aurelianense from lutionary lineage of Central European Anchith- Sandelzhausen shows that the majority of the erium aurelianense exhibits a general trend to- comparable teeth of A. a. aurelianense are dis- wards size-increase and simplification of dental tinctly smaller (see fig. 3 and 4 and ABUSCH-SIEW- pattern, however large sample-sizes are essen- ERT 1983, p. 76, fig. 15; p. 83, fig. 16). Therefore, a tial to identify subspecies, because the dentitions referral of the Bohlinger Schlucht specimen with show a wide variability in morphology and over- A. a. aurelianense seems to be more unlikely. lap in size-ranges (fig. 3 and 4 here and ABUSCH- Size differences between the younger A. a. SIEWERT 1983). steinheimense and SMNK-PAL. 6600 are less ©Staatl. Mus. f. Naturkde Karlsruhe & Naturwiss. Ver. Karlsruhe e.V.; download unter www.zobodat.at

18 carolinea, 67 (2009) pronounced, however, the m3 from Bohlinger References Schlucht is clearly wider than all known m3 from ABUSCH-SIEWERT, S. (1983): Gebissmorphologische Steinheim (fig. 4 and ABUSCH-SIEWERT 1983, p. Untersuchungen an eurasiatischen Anchitherien 218, fig. 93 and 94). The overall morphology and (Equidae, Mammalia) unter besonderer Berücksich- tigung der Fundstelle Sandelzhausen. – Courier For- size of SMNK-PAL. 6600 compares best A. a. hip- schungsinstitut Senckenberg, 62: 1-361. poides, which is known from contemporaneous BERNOR, R. L. & AMOUR-CHELU, M. (1999): 18. Family localities. Equidae. – In: RÖSSNER, G. & HEISSIG, K. (Eds): The Although a certain identification to the subspecies Miocene Landmammals of Europe: 193-202; Mün- rank is not possible for the Bohlinger Schlucht chen (Verlag Friedrich Pfeil). Anchitherium-material, the occurrence of a pos- BÖHME, M. (2003): The miocene climatic optimum: sible Anchitherium aurelianense hippoides again evidence from ectothermic vertebrates of Central underscores the MN6 correlation of this locality Europe. – Paleogeography Paleoclimatology, Paleo- ecology, 195: 389-401. (GIERSCH 2004 b). Discovery of additional mate- rial should increase the usefulness of subspecies DAXNER-HÖCK, G. & BERNOR, R. L. (2009): The early Vallesian vertebrates of Atzelsdorf (Late Miocene, for biostratigraphic and biochronologic studies. Austria) 8. Anchitherium, Suidae and Castoridae Using the mesowear method, a tool for recon- (Mammalia). – Annalen des Naturhistorischen Mu- structing palaeodietary regimes, KAISER (2009) seums Wien, 111A: 557-584. showed that the Sandelzhausen (MN5) Anchith- GIERSCH, S. (2004 a): Eine neue mittelmiozäne Wirbel- erium aurelianense were able to cope with a tierfundstelle in der Oberen Süßwassermolasse am Schiener Berg (Baden-Württemberg). – In: REITNER, rather abrasive diet. Such diet (e.g. C3 grasses or sclerophyll vegetation) probably slightly in- J., REICH, M. & SCHMIDT, G. (Hrsg.): Geobiologie 74. creased their rate in the molasse basin vegeta- Jahrestagung der Paläontologischen Gesellschaft, tion during Badenian, when the Middle Miocene Kurzfassungen der Voträge und Poster, 2004: 92; Göttingen (Universitätsdrucke). climatic optimum ends. Increasing seasonality GIERSCH, S. (2004 b): Die Fauna aus den mittelmiozä- and dryer periods (BÖHME 2003) probably led to nen Krokodilschichten der Bohlinger Schlucht, ein more open woodlands. The occurrence of drier Beitrag zur Paläoökologie und Biostratigraphie der habitats in the vicinity of the Bohlinger Schlucht Oberen Süßwassermolasse am Schiener Berg (Ba- is indicated by both micro- and macro-mammals den-Württemberg). – Carolinea, 62: 5-50. as well as molluscs (GIERSCH 2004 b). Therefore, HANTKE, R. (1954): Die fossile Flora der obermiozänen Anchitherium probably found adequate habi- Oehninger-Fundstelle Schrotzburg. – Denkschrift tats in the molasse basin and competed directly der Schweizer naturforschenden Gesellschaft, Ab- with the hypsodont equids Cormohipparion and handlungen, 2: 27-118. HEER, O. (1859): Flora tertiara helvetica. – Bd. 3; 1-378, Hippotherium after their arrival in early Valle- Winterthur. sian (MN9). Anchitherium likely became extinct KAISER, T. M. (2009): Anchitherium aurelianense (Equi- within MN9 due to a combination of competition dae, Mammalia): a brachydont „dirty browser“ in with hipparioinine (KAISER 2009) and the the community of herbivorous large mammals from change of habitats from more closed subtropical Sandelzhausen (Miocene, Germany). – In: RÖSSNER, forest to open country temperate woodlands. G. & GÖHLICH, U.: Fossillagerstätte Sandelzhausen - Contributions to the fauna I. – Paläontologische Zeitschrift, 83/1: 131-140. RUTTE, E. (1956): Die Geologie des Schienerberges (Bodensee) und der Öhninger Fundstätten. – Neues Jahrbuch für Geologie und Paläontologie, Abhand- Acknowledgements lungen, 102 (2): 143-282. We thank L. COSTEUR for the possibility to work in the UHL, D., MOOSBRUGGER, V., BRUCH, A. & UTESCHER, T. collection of the Naturhistorisches Museum in Basel (2003): Reconstructing palaeotemperatures using (Switzerland). BERNOR wishes to acknowledge fund- floras – case studies for a comparison of leaf ing from the National Science Foundation including margin analysis and the coexistence approach. – EAR0125009 and BCS-0321893 (Revealing Hominid Review of Palaeobotany & Palynology, 126: 49-64. Origins Initiative to F. CLARK HOWELL and TIM WHITE) for UHL, D., BRUCH, A. A., TRAISER, C. & KLOTZ, S. (2006): his work on this project. We gratefully acknowledge Palaeoclimate estimates for the Middle Miocene careful and constructive reviews of this manuscript by Schrotzburg flora (S Germany): a multi-method ap- G. RÖSSNER (Munich), R. ZIEGLER (Stuttgart) and H.-W. proach. – International Journal of Earth Sciences MITTMANN (Karlsruhe). (Geologische Rundschau), 95: 1071-1085.