Oioceros atropatenes ( Rodler & Weithofer, 1890 )

Kostopoulos, Dimitrios S. & Bernor, Raymond L., 2011, The Maragheh bovids (Mammalia, Artiodactyla): systematic revision and biostratigraphiczoogeographic interpretation, Geodiversitas 33 (4), pp. 649-708 : 661-667

Oioceros atropatenes ( Rodler & Weithofer, 1890)

Antidorcas ? atropatenes Rodler & Weithofer, 1890: 15 , pl. 4, fig. 8; pl. 6, figs 3-5.

Demecquenemia rodleri n. comb. basal horn-core dimensions

D. rodleri n. comb. basal horn-core dimensions at 7 cm above the base

Gazella deperdita basal horn-core dimensions

G. deperdita horn-core dimensions at 7 cm above the base

Oioceros atropatenes – Gaillard 1902: 93. — Heintz 1963: 110.

Oioceros boulei Mecquenem, 1925: 41 , text-figs 10, 11.

LECTOTYPE (designated by Bouvrain & Bonis 1985). — Right horn-core ( Rodler & Weithofer 1890: pl. 6, fig. 5).

TYPE LOCALITY. — Maragheh, Iran (late Miocene).

MATERIAL EXAMINED. — MNHN.F:Partofskull, MAR1121 ( Mecquenem 1925: pl. VII, fig. 8 as Oioceros boulei ), MAR1327; frontlet, MAR1326 ( Mecquenem 1925:pl.VIII, fig. 2 as Oioceros boulei ), 2741, 2727, 2756; isolated right horn-cores, MAR1826 ( Mecquenem 1925: pl. VII, fig.3), 2757, 2747, 2705, 2753, 2701, 2744, 2783d, 2690, 2688, 2709, 2723, 2716, 2713, 2743, 2706, 2683, 2680, 2685, 2686, 2742, 2682, 2718, 2687, 2698, 2711; isolated left horn-cores MAR2752 ,2751, 2758,2750,2681, 2699,2707, 2693, 2748, 2717, 2684, 2692, 2695, 2746, 2719, 2708, 2702, 2754, 2720, 2697, 2712, 2721, 2714, 2749, 2704, 2691, 2696; palate, MAR3141; P2-M3, MAR3146 (old label:MMTT13/1501), MAR1020;P2-P4, MAR1849, 1847; p4-m3sin, MAR2739 ( Mecquenem 1925: pl.VII, fig. 6 as Oioceros boulei ); mandible MAR1021 +1029 (Mecquenem

Kostopoulos D. S. & Bernor R. L.

TABLE 6. — Cranial and horn-core measuremens (in mm) of Demecquenemia rodleri ( Pilgrim & Hopwood, 1928) n. comb. from Maragheh. For abbreviations see text.

1925: pl. III, fig. 7, 7a as G. gaudryi ); p2-m3, MAR1841, 1856, 1860, 1164, 1026, 3149. — NHML:5 isolated unnumbered horn-cores in the Savage collection. — HUW: isolated horn-cores, MMTT13/1214, 13/nn ; P2-M3, MMTT13/1248, 13/1206, 13/1205, 13/1357, 13/1361; p2-m3, MMTT7/2435, 31/1873, 13/1300, 13/1396, 13/1372, 13/1293.

REMARKS

Spiral-horned antelopes of either clock- or anticlockwise torsion are well-documented in the Maragheh collection both in number of specimens and taxa but species level taxonomy is in many cases confusing and certainly still open to discussion. Besides Oioceros rothii ( Wagner, 1857) and O. atropatenes ( Rodler & Weithofer, 1890) , Mecquenem (1925) introduced one more species O. boulei , while later Pilgrim (1934) suggested referring the O. rothii skull illustrated by Mecquenem (1925: pl. VII, fig.7) to as a new taxon O.? mecquenemi.

Oioceros atropatenes is the most abundant species of the Maragheh bovid assemblage, represented in the MNHN.F collection by no less than 32 individuals (MNI based upon horn-cores; Tables 7; 8). Heintz (1963) addressed most of the taxonomic questions concerning the systematics of the species and gave a detailed description of the MNHN.F sample that, however, includes several additional unpublished specimens ( Fig. 8 ; Table 8).

The cranial specimen MAR1121 is badly damaged behind the orbits ( Mecquenem 1925: figs 10, 11; Table 7). The nasals are elongated comparatively to the frontals (L fr = 39.0 mm, Lnas = 48.5 mm); the lacrimal fossa is deep and round; the orbit is large and round with its anterior margin placed above the M2. The cranium MAR1327 assigned to O. boulei (Wbmas = 49.3 mm, Wbcon = 30.8 mm, W ptb = 18.3 mm, Lfp-ocp = c. 30.5 mm; Fig. 8 ; Table 7) lacks the entire face and is partly damaged ventraly. Although the basal diameters of the O. atropatenes horn-cores (Table 8) show a continuous distribution with slightly positive allometry of APD vs TD (a = 1.09; Fig. 9 ), Heintz (1963: 112) recognized two size-categories interpreted as representing sexual dimorphism. Female horn-cores are about 13-15% smaller in basal dimension, longer and less tightly twisted than male horn-cores. The great axis of the horn-core base forms a 45° angle with the sagittal plane. The horn-core compression is weak (CI: 77.8-100.8% in males, n = 39; 75.7-107.7% in females, n = 28) and usually anteroposterior (in 98% of the males and in 86% of the females). The postcornual fossa varies from rather small and shallow (63%) to large and shallow or occasionally deep. About a fourth of the specimens bear an additional fossa just above the postcornual one. In 16% of the studied cases the horn-core longitudinal axis declines from a straight line indicating a weak degree of close spiralling independently of sex, whereas in 20% of the sample the characteristic lateral furrow is barely recognized or absent. In a few specimens the horn core seems to extend onto the anterior face of the pedicle forming a “V” projection and in those cases an incipient anterior keel is present.

Apart from the upper toothrow of the specimen MAR1121 described by Heintz (1963) ( Fig. 10A ) we refer the palate MAR3141 ( Fig. 10B ) and two right P2-M3 (MAR3146, MAR1020), as well as two premolar rows, MAR1349 ( Fig. 10 C-E) and MAR1847 to O. atropatenes ( Table 4). This hypodigm shares all the morphological features defined by Heintz (1963) but with a somewhat wider size and morphological variation. The upper premolar row represents 61-68% of the molar row length ( Table 4). The upper molars have no basal pillars or central islets; their posterior lobe is square-shaped; the labial ribs are weak; the mesostyle is thin but well-developed and the parastyle is rather strong and mesially directed ( Fig. 10A, B ). The P2 and P3 are asymmetrical with weak lingual bilobation and strong, mesially placed paracone ( Fig. 10A ). The P4 is more symmetrical with strong parastyle moderately developed metastyle and weak metacone.

Heintz (1963: 111) referred to O. atropatenes the mandibular fragment with p4-m3, MAR2739 figured by Mecquenem (1925: pl. VII, figs 6, 6a) and two more specimens with m2-m3. Nevertheless, several additional lower toothrows in Paris and Washington compare closely in size to the

Kostopoulos D. S. & Bernor R. L.

TABLE 8. — Horn-core measurements (in mm) of Oioceros atropatenes ( Rodler & Weithofer, 1890) from Maragheh. For abbreviations see text.

hypodigm of O. atropatenes ( Table 5). The lower premolar row is much reduced representing 44.5- 51.5% of the molars ( Fig. 4). The lower molars have no basal pillars but a weak goat fold is present on m1 and m2 ( Fig. 10C, D ). The parastylid is strong especially on the m3 and the metastylid directs distally. The talonid of the m3 is bi-cuspid. The p3 has a narrow, pinched hypoconid, very weak paraconid that fuses quickly with the parastylid, and distally directed, short metaconid closing the posterior valley in advanced stage of wear. The p4 is quite similar to the p3 but the paraconid is occasionally stronger and the metaconid is elongated and curves distally ( Fig. 10A ); in half of the specimens the posterior valley appears closed from the first stages of wear.

The species is so far known only from Maragheh but Dmitrieva (2007) recently ascribed to it several samples from Mongolia.Nevertheless, the overall size of the Mongolian horn-core specimens (i.e. longer and rather larger than O. atropatenes ) and their morphology (i.e. more mediolaterally compressed compared to O. atropatenes , more strongly twisted, clearly lyrated and distally divergent with flattened antero-lateral basal surface) led us to reject Dmitrieva’s interpretation; we refer these horn-cores to Oioceros rothii . Furthermore, the description of O. atropatenes given by the same author does not conform with our current observations on the Maragheh sample, while the provided generic diagnosis of Oioceros neglects recent advances on the type species (i.e. Roussiakis 2003) allowing misleading conclusions.

Oioceros rothii ( Wagner, 1857)

Antilope rothii Wagner, 1857: 154 , pl. 6, fig. 20.

Oioceros rothii – Gaillard 1902: 93.

Oioceros ? mecquenemi Pilgrim, 1934: 3.

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

MATERIAL EXAMINED. — MNHN.F:Part of skull MAR2726 ( Mecquenem 1925: pl. VI, fig. 4; pl. VII, fig. 7); opisthocranium, MAR1057; frontlet MAR1320 ( Mecquenem 1925: pl.VII, fig.4), 2728, 1119, 1120, 1806+1808; right horn-core, MAR1810 (Lhc = 140 mm, TDhcb = 18.1 mm, APDhcb = 27.9 mm);lefthorn-core, MAR1809 (Lhc = 135mm, APD hcb = 25.7 mm); lower toothrows, MAR1828, 1829 ( Mecquenem 1925: pl. VII, fig. 5 as Helicophora rotundicornis ), 1890-1892, 1902, 1903, 1905 (labeled as Prostrespiceros rotundicornis ), 1907, 1846. — HUW: mandible, MMTT37/2170; left p2-m3, MMTT31/2257

Kostopoulos D. S. & Bernor R. L.

Oioceros atropatenes ( Rodler & Weithofer, 1890) , Maragheh (females)

Oioceros atropatenes, Maragheh (males) Oioceros rothii ( Wagner, 1857) , Çorak Yerler Oioceros rothii, Maragheh

Oioceros rothii, Pikermi

Oioceros rothii, Vathylakos

DESCRIPTION AND REMARKS

Much less well-known, the second Oioceros species from Maragheh is represented by finely preserved frontlets and some tooth rows ( Tables 4, 5, 7). Compared to the smaller Oioceros atropatenes , the orbits project more laterally, the postcornual fossae are rather large and shallow, the supraorbital foramina are smaller, the temporal lines are less developed, and the horn-cores are more uprightly inserted, more mediolaterally compressed, more strongly twisted (1+ coil), slightly curved backwards at the middle of their height and clearly divergent at their distal part ( Fig. 11E, F ; Table 7). Whereas in O. atropatenes the longitudinal furrows descend above the postcornual fossa at the posterolateral edge of the horn-core base, in O. rothii they originate more anteriorly on the lateral surface forming a wider zone that reaches the anterior side of the horn-core ( Fig. 11E, F ). This zone is extremely porous in the lower half of the horn-core. There is one predominant lateral furrow, instead of usually two in O. atropatenes ; this furrow forms the characteristic wrapping of the horn-core, exceptionally evident in the proximal half. A second narrow and shallow furrow appears on the upper half of the anterior surface due to the horn’s twisting. Morphological comparison between Maragheh, Axios Valley ( Arambourg & Piveteau 1929) and Pikermi ( Gaudry 1865; Roussiakis 2003) horn-core samples ( Figs 9 ; 11 ) does not show important differences; the set of the Maragheh horn-core characters is consistent with those of specimens from Pikermi described by Roussiakis (2003). The Axios Valley horn-cores have much less developed porous zone, weaker distal divergence and weaker backward curvature than the Maragheh specimens and they are also smaller on the average but not enough to be excluded from the species (contra to Bernor [1978] who referred them to O. atropatenes ). The Pikermi sample shows a greater size variation with the larger specimens (PIK2249) to be even larger than those from Maragheh (MAR1320) and the smaller ones to fit the size of the Axios Valley morph ( Fig. 9 ).

The cranium MAR2726 (Wbc = 63.2 mm, W shc = c. 7 4 m m, W bcon = 4 7.7 m m, Wbmas = 66.3 mm, LM = c. 35 mm, Wptb = 31.7 mm, H oc = 25.9 mm) is badly preserved, the horn-cores are broken at their contact with the pedicles, and a part of the parietal is missing ( Mecquenem 1925: pl. VII, fig. 7). MAR1057 retains only the occipital region. The cranial vault is globular and the top of the braincase curves down posteriorly. The face is high and the nasals are weakly domed in lateral profile. The anterior rim of the orbit is placed above the M2-M3 limit. The midfrontal suture is open and complicated. The occiput is semicircular shaped and faces postero-laterally, whereas the mastoid faces mostly posteriorly. The occipital condyles are keeled and they do not deflect significantly from the occipital level. The foramen magnum is large. The nuchal crest is weak. The basioccipital faces partly laterally, it is trapezoidal with ridge-like posterior tuberosities perpendicular to the sagittal plane and long, ridge-like anterior tuberosities trending anteroposteriorly. The foramina ovale open at the level of the anterior tuberosities of the basioccipital and face mainly laterally. The cranium MAR2726 is slightly larger than the single known skull of Oioceros rothii from the type locality of Pikermi (PG95/1502a; Roussiakis 2003) but it shares with it the high face, the domed nasals, the long and curved down posteriorly opisthocranium, as well as, the higher bi-laterally faced occiput and the longer basioccipital, characters that distinguish them from O. atropatenes .

In his discussion of the dental morphology of Oioceros rothii from Pikermi, Roussiakis (2003) excluded MAR3145 from this species (contra to Mecquenem 1925: pl. VI, fig. 2) and included in it the mandible MAR1828 (type of Antidorcas ? gaudryi Mecquenem, 1908 ; Mecquenem 1925: pl. VII, figs 5-5a); we agree with this attribution ( Tables 4, 5). Both the upper and lower dental morphologies of Maragheh O. rothii are very similar to those from Pikermi ( Roussiakis 2003) except perhaps for the stronger and more frequent basal pillars that appear in all upper molars of MAR2726 and in several m1 and m2 but less often on m3. Furthermore, the paraconid is still present in half of the preserved p4 and in a few p3 from Maragheh. The lower premolars represent 57-62% of the molar row length ( Fig. 4; Table 5).

Figures

FIG. 8. — Oioceros atropatenes (Rodler & Weithofer, 1890) cranium (MNHN.F.MAR1327) from Maragheh in lateral (A), occipital (B), ventral (C) and dorsal (D) views. Scale bar: 5 cm

FIG. 9. — Bivariate plots of basal horn-core dimensions (in mm) in Oioceros Gaillard, 1902 (transverse diameter [TD] against anteroposterior diameter [APD]). Data for Çorak Yerler, Turkey from KÖhler (1987).

FIG. 10.— Oioceros atropatenes (Rodler & Weithofer,1890) dentitions from Maragheh:A, P2-M3 sin (MNNHP MAR1121) in occlusal view; B, P2-M3 dex (MNHN.F.MAR3146) in labial view; C-E, right mandibular ramus (MNHN.F.MAR3149) in occlusal (C), labial (D) and lingual (E) views. Scale bars: 2 cm.

FIG. 11. — Comparison of Oioceros rothii (Wagner, 1857) horn-cores from: A, B, Axios Valley (MNHN.F.Slq794); C, D, Pikermi (MNHN.F.PIK2244); E, F, Maragheh (MNHN.F.MAR1320); A, C, E, frontal views; B, D, F, caudal views. Scale bar: 5 cm.