Tragoportax sp.

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 : 472

Tragoportax sp.

FM-2094 ( Fig. 13H ) is the poorly preserved skull of a large Tragoportax Pilgrim, 1937 preserving the splanchnocranium (without the rostral part) as well as the basal half of the horn-cores (measurements: Table 4). The shape and divergence of both horncores are symmetrical,showing that they do not result from post-mortem deformation. There is a deep, large anteorbital fossa. The intercornual distance is large (about 42 mm): in frontal view the bases of the horn-cores make with the frontal bone a Ushaped figure, as in T. rugosifrons (Schlosser, 1904) (not V-shaped as in T. amalthea (Roth & Wagner, 1854)) . The horn-cores are strongly divergent at the base (about 70 degrees), and this divergence increases upwards. In lateral view the anterior edges of the horn-cores are strongly curved backwards. The posterior surfaces are damaged and the shape is not clear, but it seems that the posterior borders are also arched, not straight, and the medial side is clearly convex. The anterior keels of the horn-cores lack rugosities and steps, but from the damaged frontal bone it seems that the keels extend onto the frontals for about 1/3 of the orbit diameter. The increase of divergence of the horn-cores is stronger than in T. rugosifrons ; at Hadjidimovo, only a few specimens have a slight normal torsion of the keel ( Spassov & Geraads 2004). This morphology could be derived for Tragoportax , as it is reminiscent of T. amalthea , although it is also less expressed in this species, which has horn-cores closer to each other, and with steps along the anterior keel; FM-2094 is more similar to T. rugosifrons in these features, but T. rugosifrons (that is well represented at Hadjidimovo) has less divergent and less backwardly curved horn-cores, with much weaker torsion of the keels and the convex horn-core surface is the lateral instead of the medial one.

The frontlet figured as T. amalthea by Andree (1926: pl. 10, fig. 5) with its long twisted horncores also has some similarities with the skull from Strumyani, but the most similar to the latter are the skull PXM-93 from the early Turolian of Prochoma, Greece referred to T. rugosifrons by Bouvrain (1994), with its backwardly curved horn-cores and torsion of the anterior keel, and perhaps also the unpublished material from Molayan.

There are also a right mandible with p4-m3, FM-2758 (L m1-m3 = 67 mm), and another one, FM-2737, with p3-m3 and the roots of p2, probably its counterpart. The teeth are much worn and identification is not straightforward, especially as the metaconid of p4 is more expanded lingually than is usual in Tragoportax , but the presence of basal pillars and of convex lingual walls on the molars fits better this genus than similar-sized members of the Protoryx-Pachytragus group. The latter have much shorter premolars than Tragoportax , but this is mostly due to their small p2, absent here. We also assign to Tragoportax several maxillary and mandibular remains with the size and morphology of Tragoportax ( Spassov &Geraads 2004) :a maxilla, FM-2155, with DP3-M3 (M3 unerupted; M1-M3 = 63.5 mm.); mandibles and mandibular fragments, FM-2154, FM-2219 (Lm3 = 29.5), FM-2338 (Lm3 = 28), FM-2294 (Lm3 = c. 30); an astragalus, FM-2121 (H = c. 51, dist. TD = c. 33), and a proximal metacarpus, FM-2425 (TD = 39.3).

Figures

FIG. 13. — Fossil mammals from the Miocene of Strumyani (SW Bulgaria): A-C, F, G, Palaeoreas lindermayeri Wagner, 1848; A, skull FM-2738, front view; B, mandible FM-2744; C, mandible FM-2783; F, frontlet FM-2740; G, frontlet FM-2780; D, I, J, Prostrepsiceros rotundicornis (Weithofer, 1888); D, mandible FM-2331; I, frontlet FM-2779; J, frontlet FM-2739; E, Palaeoryx sp., tooth row p2-m2 FM-2251; H, Tragoportax sp., skull FM-2094. Scale bar: A, G-J, 20 cm; B-E, 5 cm.