Dihoplus pikermiensis (Toula, 1906)

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 : 460

Dihoplus pikermiensis (Toula, 1906)

The best specimen is skull FM-2469, which is complete but with a bone surface that is heavily eroded and fragmented ( Geraads & Spassov 2009: fig. 2, pl. 1, G, H). It clearly displays all the features by which the skull of this species can be distinguished from that of Ceratotherium neumayri (Osborn, 1900) ( Geraads 1988; Geraads & Spassov 2009), such as the sharp ventral orbital border, the shortened cranial basis with the post-tympanic overlapping the post-glenoid process, and a constricted protocone on the molars. The rarely preserved premaxillae are complete, and show no trace of incisors. Such incisors are large in its likely ancestor D. schleiermacheri (Kaup, 1832) , and may still occasionally be found in D. pikermiensis .

The mandible FM-2470, found close to the skull and probably belonging to the same individual, has a straight ventral border, unlike C. neumayri , and a pair of large incisors ( Fig. 3D ), much smaller than in D. schleiermacheri , but less reduced than in other specimens of D. pikermiensis . Measurements are given in Table 2.

In Bulgaria, D. pikermiensis is also present at Kalimantsi and common at Hadjidimovo. It is also quite common in its type-locality, Pikermi, and has also been described from several other Turolian localities of the Aegean region ( Geraads 1988, 1994; Giaourtsakis 2003, 2009; Giaourtsakis et al. 2006; Geraads & Spassov 2009). At Str-2, the absence of upper incisors,and the presence of relatively large lower ones, suggest an age slightly earlier than Pikermi, if we are correct in assuming a trend towards reduction of the incisors.

Figures

FIG. 3. — Fossil mammals from the Miocene of Strumyani (SW Bulgaria): A-C,?Tetralophodon atticus (Wagner,1857); A, DP2 FM-2027, occlusal view;B, dp2 FM-2799, lingual view,C, DP3 FM-2798,occlusal view; D, Dihoplus pikermiensis (Toula, 1906), dorsal view of symphysis FM-2470;E, Microstonyx major (Gervais,1848),maxilla FM-2801;F, G, Dorcatherium cf.puyhauberti Arambourg & Piveteau,1929, mandible FM-2741 in occlusal (F)and lateral (G) views;H, Palaeotragus rouenii Gaudry,1861,mandible FM-2778;I, Miotragocerus (Pikermicerus) gaudryi (Kretzoi,1941), mandible FM-2103; J, Cervidae gen.et sp. indet., mandible FM-2100. Scale bar: A-C,F-J, 7.5 cm; D, 30 cm; E, 10 cm.