Hippotherium Kaup, 1832

Geraads, Denis, Kaya, Tanju & Mayda, Serdar, 2005, Late Miocene large mammals from Yulafli, Thrace region, Turkey, and their biogeographic implications, Acta Palaeontologica Polonica 50 (3), pp. 523-544 : 531-534

Genus Hippotherium Kaup, 1832

Type species: Equus primigenius von Meyer, 1829 ; Eppelsheim , Germany, Vallesian, Miocene .

Hippotherium cf. primigenium (von Meyer, 1829) dium size. The third phalanx (Fig. 10G) is well preserved with small splits around the sole. Material from Yulafl I.—Five isolated upper cheek teeth, two isolated lower cheek teeth, three isolated incisors, two Mc−III Comparisons.—The Hippotherium remains from Yulafli are (TTMEU−CY−18, CY−200), two astragali (TTMEU−CY−19, too incomplete for precise specific identification. Their char− TTMEU−CY−19a), calcaneus (TTMEU−CY−118), phalanx−2 acters fit those of H. primigenium from Eppelsheim (Bernor (TTMEU−CYA−4), phalanx−3 (TTMEU−CYA−9). Measure− et al. 1996), but they are smaller and the metacarpal is gracile ments: Table 3. and less massive (especially distally). The index (11/1) of Mc−III is smaller than those of H. primigenium from Eppel− Description.—On the upper teeth (Fig. 10A–E), the proto− sheim (174) and Vienna Basin (165–194) ( Sondaar 1974; cone is lingually flattened, and more lingual than the hypo− Bernor et al. 1988), but closer to that (157) of Rudabánya cone. Its length varies from 7.5 to 6.1 mm. The hypocone is ( Bernor et al. 1993). Hippotherium primigenium from Ravin triangular and encircled by a deep hypoglyph. The upper de la Pluie has some morphological similarities with that cheek teeth have richly plicated enamel. The folds (24 on the from Yulafli, but the plication number is low (17 for M1–2) molars) are deep, narrow, and almost parallel. The posterior and the metacarpal III is short and robust ( Koufos 1986). The wall of the postfossette is distinct. The pli caballin is complex teeth from Yulafli are similar to those of H. primigenium or bifid. The lower teeth have a small protostylid at occlusal from the Vallesian of Nesebar in Bulgaria, but the metacarpal level, but no ectostylid, a triangular−rounded metaconid, and III is slightly more massive ( Forstén 1978). The maxillary crenulated enamel in the flexids. The hypsodonty index (HI) teeth of H. primigenium from Dorn−Dürkheim 1 (Kaiser et al. can be calculated for a few teeth (for upper molars 181–217; 2003 pl. 1) share some morphological similarities with the for one upper premolar 186) and their values show moder− Yulafli material, but differ in their wider maxillary teeth, ately hypsodont teeth. The lower incisor (I 1 = 15 × 10.3 mm) shallower hypoconal groove, and larger size. has crenulated enamel on the occlusal surface. The material of Yulafli is similar to that of the Vallesian The Mc−III (Fig. 10F) is short and rather slender ( Fig. 11 ), of Eşme−Akçaköy in the TTMEU Izmir, in having highly orespecially distally, with low robustness indices (11/1) of 141 namented pre−and postfossette, a complex pli caballin, and a and 154 for two Mc−IIIs. The keel index (12/13) is 111 and moderate hypsodonty. However, the latter differs from our 113, respectively. The astragalus and calcaneus are of me− sample by its larger size, the occurrence of a protocone spur, +

Fig. 10. A–G. Hippotherium cf. primigenium . A. TTMEU−CY−50, right P3–4. B. TTMEU−CY−123, left M1–2. C. TTMEU−CY−20, left M1–2. D. TTMEU−CY−51, right M1–2. E. TTMEU−CYA−7, left M3. F. TTMEU−CY−200, Mc−III in anterior view. G. TTMEU−CYA−9, Phalanx−III in dorsal (G 1) and lateral (G 2) views. H, I. Dorcatherium cf. jourdani . H. TTMEU−CY−139, left m 3 in occlusal view. I. TTMEU−CY−141, left dentary in lateral (I 1) and occlusal (I 2) views. J, K. Hippopotamodon antiquus . J. TTMEU−CY−45, symphysis and front teeth in dorsal (J 1) and right lateral (J 2) views. K. TTMEU−CY−49, right tooth−row in occlusal view, stereo. All from Yulafli, Turkey, Vallesian, late Miocene.

the deeper hypoconal groove, the confluent distal wall of the postfossette, and stouter metacarpals ( Fig. 11 ). The Mc−IIIs from Yulafli are also smaller and less massive than the Mc−IIIs from Eppelsheim and Rudabánya. The Yulafli hipparion differs from both Cormohipparion sinapensis and “ H”. ankyranum from Sinap Tepe ( Ozansoy 1965; Bernor et al. 2003) in the following characters: the maxillary cheek teeth have highly ornamented pre−and postfossette, the protostylid is present in the lower teeth, and the metacarpal III is lightly built ( Bernor et al. 2003: fig. 11.8). They share a lingually flattened protocone, a deep distal hypoconal groove, a complex or bifid pli caballin, and a distinct posterior wall of the postfossette. However, the Mc−IIIs from Sinap Tepe have very diverse proportions, and some specimens from Loc. 12 (early MN 10), conform well with our specimens in being short and slender ( Fig. 11 ); they were referred by Bernor et al. (2003) to “ Hipparion ” sp. 1, while slightly stouter specimens from Sinap Loc. S01 were identified as aff. “ Hipparion ” kecigibi.

Our material is also distinct from the H. aff. depereti from Pentalophos ( Koufos 2000), which has teeth with moderate enamel plications (19 for M1–2) and short massive metacarpals (the index 11/1 = 170). The teeth from Yulafli certainly differ from the Turolian hipparions of Gülpinar and Kemiklitepe (TTMEU), where the enamel plication is simple, the protocone is rounded, and the pli caballin is simple. The keel index of Mc−IIIs is 111–113 indicating Vallesian forms ( Sen et al. 1978; Staesche and Sondaar 1979) from that of the Turolian forms.

Similarities in dental morphology indicate that the Yulafli hipparion is closer to Vallesian forms than to Turolian ones, but the Mc−IIIs are smaller and less massive. These characters suggest that it is more advanced than early Vallesian forms of H. primigenium .

Figures

Fig. 11. Plot of length versus distal articular width of Mc−III in some hipparions.