Hipparion dietrichi (Wehrli, 1941)

Geraads, Denis, Spassov, Nikolaï, Hristova, Latinka, Markov, Georgi N. & Tzankov, Tzanko, 2011, Upper Miocene mammals from Strumyani, South-Western Bulgaria, Geodiversitas 33 (3), pp. 451-484 : 461-462

Hipparion dietrichi (Wehrli, 1941)

There are two relatively well preserved skulls of this species. FM-2029 is a subadult individual, with unerupted I3s, C and M3 just erupted ( Fig. 6C ). FM-2030 belongs to an adult individual, but is not well-preserved, so that some of the characters described are those of FM-2029. The muzzle is short and broad. The nasal slit ends above the anterior end of P2; the crista facialis reaches the middle of P4; the choanae reach the limit M1-M2; the orbit is above the posterior half of M3. The anteroposteriorly oriented preorbital fossa is small and shallow, without posterior pocket and with a weak anterior rim. It extends from above the anterior part of P3 to above the posterior border of M1. The infraorbital foramen is large, located below the anterior border of the fossa. Tooth row length is about 136 mm for FM-2029 and 153 mm for FM-2030. There is no DP1. The anterostyle of P2 is elongated. The enamel is moderately plicated, with rounded folds whose number ranges from 14 on the premolars to 21 on the molars. The pli caballin is single. The protocon is oval, and lenticular on the less worn teeth. The hypocone is elongated, angular on P4; the hypoconal sinus is comparatively deep in the subadult skull and medium to absent in the adult one.

The short and broad muzzle, antero-posteriorly oriented oval preorbital fossa without well defined peripheral rims and without posterior pocket, relate this skull to H. dietrichi , and the tooth features support this conclusion. Hipparion dietrichi is known from many localities in Greece, Turkey and Republic of Macedonia ( Koufos 1987c, 1988; Forstén & Garevski 1989; Vlachou & Koufos 2002, 2006, 2009; Koufos & Vlachou 2005). From its muzzle length the skull from Str-2 is close to H. dietrichi from AkkasdaĞI, but in cheek tooth length it is intermediate between the Perivolaki and Vathylakkos samples on the one side and the AkkasdaĞI form on the other ( Koufos 1988; Koufos & Vlachou 2005; Vlachou & Koufos 2006).

Figures

FIG. 6. — Fossil mammals from the Miocene of Strumyani (SW Bulgaria): A, Hippotherium cf. brachypus (Hensel, 1862), lateral view of skull FM-2326; B, Cremohipparion mediterraneum (Roth & Wagner, 1855), lateral view of skull FM-2028;C, Hipparion dietrichi (Wehrli, 1941), lateral view of skull FM-2029. Scale bar: 20 cm.