Prostrepsiceros fraasi ( Andree, 1926 )

Kostopoulos, Dimitrios S. & Bernor, Raymond L., 2011, The Maragheh bovids (Mammalia, Artiodactyla): systematic revision and biostratigraphiczoogeographic interpretation, Geodiversitas 33 (4), pp. 649-708 : 674-676

publication ID	https://doi.org/ 10.5252/g2011n4a6
persistent identifier	https://treatment.plazi.org/id/03EE374D-575C-C95C-FCAF-FBE9FC07FE25
treatment provided by	Marcus
scientific name	Prostrepsiceros fraasi ( Andree, 1926 )
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Prostrepsiceros fraasi ( Andree, 1926) ( Fig. 13 View FIG A-D)

Helicoceras fraasi Andree, 1926: 163 , pl. 11, fig. 4; pl. 15, fig. 1.

Helicophora rotundicornis – Mecquenem 1925: 39.

Prostrepsiceros rotundicornis – Gentry 1971: 265 partim.

TYPE LOCALITY. — Samos, Greece (late Miocene).

MATERIAL EXAMINED. — MNHN.F: A partial cranium, MAR1310; opisthocranium, MAR1060, 1059 juvenile; frontlet, MAR1010, 1306 ( Mecquenem 1925: pl. VII, fig. 1 as Helicophora rotundicornis ), 1322, 1318; isolated horn-cores, MAR1002, 2094, 1817, 1833; P2-M1, MAR2111; P3-M3, MAR2127; P4-M2, MAR1961, 1934; P4-M3, MAR3236; p2-m3, MAR3179; p3-m3, MAR3219; p4-m3, MAR1895.

DESCRIPTION AND REMARKS This is probably one of the most confusing bovid taxa in the Maragheh assemblage, referred either to Prostrepsiceros rotundicornis (Weithofer, 1888) (i.e. Rodler & Weithofer 1890; Gentry 1971; Solou-

nias 1981; Watabe 1990) or to P. fraasi (i.e. Andree 1926; Bouvrain 1982; Bouvrain & Thomas 1992). Mecquenem (1908) originally described this spiral horned antelope as a new species Antidorcas ? gaudryi but he later ( Mecquenem 1925) changed his mind referring it to Pr.rotundicornis . Apart from the frontlet illustrated by Mecquenem (1925: pl. VII, fig. 1) the species is documented in the Maragheh collection of Paris by several additional cranial and dental specimens representing at least 8 individuals ( Fig. 13 View FIG A-D; Tables 4, 5, 12). More material has been published by Watabe (1990: 25, pl. III, figs 1, 2), whereas part of the P. houtumschindleri sample discussed by Bernor (1978) might belong to this species as well.

In distinction from P. houtumschindleri , the greatest axis of the horn-core base forms a 50-70° angle with the sagittal plane, whereas at 7 cm above the base the same axis is trending medio-posteriorly to antero-laterally forming a 30° angle with the sagittal plane. The mean horn-core compression index is 122% at the base (CI: 107.3-134.7; n = 9) and 84% at 7 cm above the base (CI: 77.8-88.9; n = 7) ( Fig. 14 View FIG , Table 12). The horn-cores are more uprightly inserted on the frontals than in P. houtumschindleri ( Fig. 13A, B View FIG vs E), their divergence is much stronger even from the base ( Fig. 13D View FIG vs G), the spiralling is widely open and the twisting less intense. None of the nine studied Paris specimens

Kostopoulos D. S. & Bernor R. L.

has either a posterior keel or grooving, whereas all bear a very weak anterior keel descending anteromedially to medially. In contrast to P. houtumschindleri the supraorbital depressions are placed close to the horn-core base (11.5-15.0 mm), the braincase is higher and more globular but of the same length, the occiput is higher ( Fig. 13C View FIG vs F), the external occipital crest is ridge-like, the occipital condyles protrude downwards, the basioccipital is comparatively longer, the paroccipital processes project more ventrally, and the lacrimal fossa is rather deeper.

In comparison with P. houtumschindleri , the toothrows ascribed to this species ( Fig. 4; Tables 4, 5) exhibit less developed and more centrally placed paracone on P3 and P4, strong metastyle on P4 (absent in P. houtumschindleri ), anteroposteriorly developed metaconid on p4 and narrower lower molars with weaker entostylid.

The cranial and horn-core features of the Maragheh species are much closer to those of P. fraasi from Samos than to P. rotundicornis from Pikermi, which is characterized by shorter opisthocranium, shorter and more robust horn-cores that are less uprightly inserted on the frontals, more closely spiralled, taper faster upwards, and show more developed accessory features (keels, grooves). The single known skull of P. fraasi from Samos shows some features that are probably more advanced than the Maragheh morph (i.e. stronger cranio-facial angle, slightly shorter opisthocranium, stronger temporal lines, strong-crest-like midfrontal and fronto-parietal sutures, absence of postcornual grooves and keel traces) but those characters are not worth species distinction and may represent time or local variation.