Prostrepsiceros, Forsyth-Major, 1891

Kostopoulos, Dimitris S. & Sen, Sevket, 2016, Suidae, Tragulidae, Giraffidae, and Bovidae, Geodiversitas 38 (2), pp. 273-298 : 289-290

Prostrepsiceros sp.

( Fig. 10 )

MATERIAL EXAMINED AND MEASUREMENTS. — Küçükçekmece West: left horn-core,MNHN.F.TRQ639 (HCBTD = 18.8 mm; HCBAPD = 24.9 mm); part of left horn-core, TRQ640 (HCBAPD = 25.7 mm). Provisionally attributed: part of right mandibular ramus with p4-m3, TRQ412 (p4:L = 8.5 mm, W = 5.0 mm; m1: L = 9.2 mm,W = 6.7 mm; m2: L = 11.2 mm, W = 8.4 mm; m3: L = 16.2 mm, W = 8.2 mm)

Küçükçekmece East: part of right horn-core, ITU no No. (HCBTD = 28.4 mm; HCBAPD = 29.6 mm);

Rami Sand Quarry: part of horn-core, ITU no No. (HCBTD = 23.8 mm; HCBAPD = 25.9 mm).

DESCRIPTION AND REMARKS

The most complete but strongly weathered specimen MNHN.F.TRQ639 ( Fig. 11A ) indicates a small heteronymous spiral-horned antelope with short, fast tapering horn-cores (preserved length along the anterior face c. 100 mm). In lateral view, the horn-core is smoothly curved posteriorly and then quickly re-curved upwards. It is placed above the orbit and bears traces of an anterior furrow. The torsion is loose and the spiralling closed. The supraorbital foramen opens into a pit, close to the base of the pedicel ( Fig. 11A ). MNHN.F.TRQ640 is a part of a horn-core just above the pedicel. Although somewhat larger, it shows the same morphological features as the previous specimen; additionally a furrow is clear along its anterior face. Horn-core specimens from Küçükçekmece East and Rami Sand Quarry are similar in size and morphology to those from Küçükçekmece West.

A single mandibular fragment (MNHN.F.TRQ412; Fig.11B ) could be attributed to this species. The paraconid of the p4 directs distally and the metaconid mesially, so the valley between them tends to be closed though it remains narrowly open until late stage of wear. The hypoconid of the p4 is well developed. The lower molars show a weak mesial fold and a short and thin basal pillar. The metastylid is weak. The entostylid is as strong as the parastylid. The buccal end of the hypoconid is angular.

Among numerous late Miocene heteronymously spiralhorned antelopes, Prostrepsiceros rotundicornis (Weithofer, 1888) from Pikermi and Chomateres (MN12, Greece), Prostrepsiceros fraasi (Andree, 1926) from Maragheh and Samos (MN11-12, Greece) and Sinapodorcas incarinatus Bouvrain, Sen & Thomas, 1994 from Yassiören, and Loc. 91 of Middle Sinap (MN9-10, Turkey) show keel-less and helicoidally spiralled horn-cores with heteronymous torsion, similarly to the Küçükçekmece species ( Bouvrain et al. 1994; Gentry 2003; Kostopoulos 2005). The spiralling is, however, much more open in Pr. fraasi and S. incarinatus , placing the Küçükçekmece form morphologically closer to Pr. rotundicornis .

Pr. rotundicornis is exclusively known from Turolian faunas of the Greco-Iranian province but Gentry (2003) attributes to this species a right horn-core from the late Vallesian Locality 63 of Middle Sinap. This early form differs from the typical Pikermi species in its smaller size and the shorter and faster tapering horn-cores that are less divergent, more inclined backwards and less obliquely inserted on the frontals ( Gentry 2003). In these features the Loc. 63 species clearly approaches the Küçükçekmece one, which, however, lacks (but also possibly due to weathering) evidences of a keel descending to a posterolateral insertion. Both the Küçükçekmece and Loc. 63 samples show a parasagittal long diameter of the horn-core, distinct from the more oblique diameter seen in the Turolian representatives Pr. rotundicornis .

Basal horn-core dimensions of the Küçükçekmece and Loc. 63 specimens are placed in between those of Pr. rotundicornis from Pikermi and the latest Vallesian Pr. syridisi Kostopoulos & Koufos, 1996 from Nikiti-1 ( Greece; e.g., Koufos et al. 2016 for a recent review). Similarly with the studied sample, the horn-cores of Pr. syridisi show anteroposteriorly trending great basal axis, tight spiralling, no anterior and a blunt posterior keel, but the horn-cores are certainly longer, and their mediolateral compression stronger (compression index is 71-83, n = 10 in Nikiti-1 versus 75.5-96, n = 3 in Küçükçekmece, and 85, n = 1 in Loc 63). As the material is very poor for definite conclusions, we suggest referring both the Küçükçekmece and Loc. 63 forms to as Prostrepsiceros sp.

Figures

FIG. 10. — Prostrepsiceros sp. from Küçükçekmece West,Turkey: A, left horncore,MNHN.F.TRQ639 in frontal (left) and medial (right) views;B, right mandible, MNHN.F.TRQ412 in occlusal (up) and lingual (down) views. Scale bars: 2 cm.

FIG. 11. — A, cf. Majoreas from Rami Sand Quarry; B-E, Majoreas cf. elegans from Küçükçekmece West, Turkey. A, proximal horn-core, ITU350 dex in frontal (left) and lateral (right) views; B, proximal horn-core, MNHN.F.TRQ637 dex in medial view; C, proximal horn-core, MNHN.F.TRQ636 dex in frontal view; D, distal horn-core, MNHN.F.TRQ634 dex in frontal view; E, p3-m2, ITU369 in buccal view. Scale bars: 2 cm.