Chilotherium sp.

Antoine, Pierre-Olivier & Saraç, Gerçek, 2005, Rhinocerotidae (Mammalia, Perissodactyla) from the late Miocene of Akkașdağı, Turkey, Geodiversitas 27 (4), pp. 601-632 : 619

Chilotherium sp.

MATERIAL. — Left calcaneus, AK6-60.

DESCRIPTION

Calcaneus

AK6-60 shares most of the characters with the two calcanei attributed to Acerorhinus sp. (AK6- 130, AK7-98; see below), but it is thicker, shorter and smaller (Appendix: Tables 32; 35). AK6-60 bears a large and concave fibula-facet; the cuboidfacet is circular and saddle-shaped, with a postero-lateral salient tip. The presence of deep vascular prints on the postero-distal side of the processus calcanei further distinguishes this specimen from the other ones unearthed at Akkasdagw ı ( Fig. 5F, G ).

DISCUSSION

All these features (size, proportions, thickness, fibula-facet and vascular prints) are common with the calcaneus 06-AKK-019 from Kavakdere (MN 12; Turkey), referred to Ch. habereri Ringström, 1924 by Saraç (1994: pl. 14, fig. 1). Both specimens belong probably to the same taxon. Ch. habereri is a small and robust Chilotherium species , with strongly shortened limbs and hypsodont teeth, originally described in the early Turolian of China ( Ringström 1924; Heissig 1975a). Some Turkish remains, ranging from the late Vallesian up to the middle Turolian, were attributed to this species in the last decades (Kayadibi and Garkın faunal sets: Heissig 1975a, 1996; Kınık faunal set: Saraç 1994). Fortelius et al. (2003: 291) describe a single tooth and a juvenile mandible from Loc. 49 (Igbek, North Central Anatolia; c. 9.1 Ma), referring them to “ Chilotherium cf. C. habereri ” and assuming that this isolated tooth “probably represents the Anatolian form that Heissig (1975a, b, 1996) referred to C. habereri ”. On the other hand, Fortelius et al. (2003: 292) consider that younger remains “from the Upper Kavakdere Locs. 34 and 26” [c. 8.4-8.1 Ma, i.e. slightly earlier than Akkasdagw ıs belong to an “indeterminate Chilotherium ”, rather than to Ch. habereri as previously assumed by Saraç (1994).

Specific features within Chilotherium are essentially based on cranial, mandibular, and dental comparison (e.g., Fortelius et al. 2003). As the available material from Akkasdagw ı is restricted to a single calcaneus (AK6-60) and pending a revision of the whole genus, we provisionally identify it as Chilotherium sp. , following the proposition of Fortelius et al. (2003).

Figures

FIG. 5. — A-E, Stephanorhinus pikermiensis (Toula, 1906), AkkaSdağı (Anatolia, Turkey), middle Turolian; A, distal end of a right radius (GOK-14), posterior view, displaying the diagnostic horizontal ridge; B, C, right magnum, lacking the posterior tuberosity (GOK-12); B, medial view; C, anterior view; D, E, left MtIII (AKA-45); D, anterior view; E, lateral view. Notice the fusion of the MtIVfacets, visible in E; F, G, Chilotherium sp., AkkaSdağı (Anatolia, Turkey), middle Turolian, left calcaneus (AK6-60); F, antero-medial view; G, posterior view. The Y-shaped vascular print is noticeable in G. Scale bar: 5 cm.