Gazella cf. capricornis (Wagner, 1848)

Kostopoulos, Dimitris S., 2005, The Bovidae (Mammalia, Artiodactyla) from the late Miocene of Akkaşdağı, Turkey, Geodiversitas 27 (4), pp. 747-791 : 748-751

Gazella cf. capricornis (Wagner, 1848)

MATERIAL EXAMINED. — Part of skull: AK5-598, AKB- 29, AK2-443; frontlets: AK2-72B, AK2-68, AK2-444, AK4-78, AK5-600, AK5-602, AK5-599, AK6-293, AK12-72; isolated horn-cores: AK2-72Asin, AK2- 153dex, AK2-154dex, AK2-44Bsin, AK2-447dex, AK2-446, AK2-449, AK2-450dex, AK2-455sin, AK2- 66dex, AK2-67sin, AK2-71sin, AK2-76dex, AK3- 120sin, AK3-71sin, AK3-193dex, AK4-74, AK4-79, AK5-190dex, AK5-603sin, AK5-640dex, AK6-65sin, AK6-66sin, AK6-67dex, AK7-163dex, AK7-30dex, AK11-60, AK11-76, AK13-24dex, AK14-15, AKK- 193sin, AKK-76, AKK-98, GOK-188, GOK-189; upper toothrows: AK6-82sin, AK6-224dex, AK6- 157sin, AK7-32dex, AK3-169dex, AK12-73sin, AK12- 74dex, AK12-76dex, AK13-25dex; lower toothrows: AK2-65sin, AK3-77sin, AK3-189sin and dex, AK3- 301dex, AK4-89dex, AK12-83sin, AK5-205sin, AK5- 206sin, AK5-262dex, AK5-257sin, AK6-73sin, AKB- 72, AKB-93, GOK-211.

Tentatively attributed: distal part of humerus: AK3- 191, AK4-82, AK5-46; proximal part of radius: AK3- 192, AK7-174; metacarpals III+IV: AK6-309, AK4-205 (young); astragals: AK4-84, AK4-83, AKK- 198, AK7-177; calcaneum: AK3-74; proximal part of metatarsals III+IV: AK4-122, AK7-106; phalanx I: AK6-84, AK11-4, AK3-195, AK4-87.

DESCRIPTION

Skull

The description of the skull morphology is based on the specimens AKB-29, AK5-598 and AK2-443

(Appendix: Table 1). In lateral profile the braincase is slightly convex ( Fig. 1A ). The interparietal is large. The face bends on the cranial roof at an angle of about 140° (AK5-598). The frontals form two shallow depressions at the postero-medial side of the pedicles. The frontoparietal and interfrontal sutures are open and the latter one appears slightly constricted between the horn-cores. The pedicles are relatively high. The supraorbital foramens are placed into triangular pits. The postcornual groove is elongated and usually deep. The orbit is large and rounded ( Fig. 2A ). Its anterior end is placed above the anterior lobe of M3. The lacrymal fossa is shallow and wide. The infraorbital foramen opens above the limit P2-P3. The palate is deep. The choane opens behind M3 and the median indent behind the lateral one. The angle basioccipitalocciput is 82° (AKB-29). The occiput is low and pentagonal shaped with strong nuchal crest. The occipital foramen is large comparatively to the condyles. The elongated and narrow paroccipital processes are curved medially. The auditory bulla is large (length 27 mm in AKB-29 and 20 mm in AK5-598) and its posterior end is placed slightly behind the posterior tuberosities. The general shape of the basioccipital is trapezoid ( Figs 1B ; 2B ). The posterior tuberosities are large, crest-like and vertical to the sagittal plane. The anterior tuberosities are smaller, sub-rounded and bulbous with their greater axis parallel to the sagital plane. A wide furrow is formed between them. The oval foramen is large, opening just in front of the anterior tuberosities.

Horn-cores

The horn-cores are relatively short and robust, inserted just above the orbits, moderately tilted (≈ 75° with the cranial roof) and smoothly curved backwards ( Figs 1A ; 3A ); the curvature index (“Length along the anterior face of the horn-core against height of its posterior face × 100”) varies between 116 and 136 (n = 7). The lateral face of the horn-cores is flat and the internal one slightly convex. They are widely separated on the frontals (internal distance at the base between 22.3 and 28.0 mm; Fig. 3B ). Their average divergence angle is about 25° (22-27°) but the degree of divergence increases from the base (almost parallel) to the top (strongly directed laterally). The cross section passes from elliptical at the base to round towards the tips (Appendix: Table 2). The anterior and posterior surfaces of the horn-cores bear one to three deep longitudinal grooves. One of them, placed in a posterocentral position, seems to be the most stable.

Although the horn-core general morphology follows the above-mentioned characters, their development varies considerably, affected mainly by ontogenetic growth. The mean length of young adults and adults is 117.4 mm (n = 18), varying between 105 and 125 mm. Young individuals present shorter horn-cores (90-100 mm). The mean index DT × 100/DAP is 80.76 at the base and 85.94 at 7 cm from the base, indicating a reduction of the mediolateral compression from the base to the top. Excluding young individuals these values slightly decrease (80.41 and 85.68 respectively). DAP b presents a negative allometry in relation to DT b (a = 0.85), which means that the transverse diameter increases more rapidly that the anteroposterior one. This is mainly true for adult individuals (a = 0.6) while the relation is rather isometric in the young ones (a = 1.05). On the contrary, at 7 cm from the base, the regression presents a plasmatic isometry (a = 1.03) for the total sample, being always negative for the adults (a = 0.78) but strongly positive for the youngs (a = 1.27). In other words it seems that the anteroposterior diameter increases more rapidly in the immature individuals than in the adults.

Dentition

The skull specimens AK5-598 and AK2-443 preserve their upper dentition, helping the determination of isolated toothrows (Appendix: Tables 3; 4). The premolar row is short comparatively to the molars; the premolar/molar ratio varies between 67.7 and 74.6 for the upper toothrow and 55.2 and 56.4 for the lower one. P2, 3 are slightly bilobed and asymmetrical. There is no basal pillar on the upper molars; their paracone is strong and the metastyle weak.

The paraconid and the parastylid are independent in the upper half of the lower third premolar crown. The metaconid directs backward and fuses with the entoconid. p4 is similar with p3 but the metaconid, entoconid and entostylid fuse together more rapidly. m1 and m2 bear a small basal pillar ( Fig. 5B ). m3 has a strong parastylid. The talonid of m3 has flat lingual face and bears a strong postero-lingual stylid.

Postcranials

Although the available postcranials attributed to Gazella are quite numerous, there is no way to be distinguished at species level.

Figures

FIG. 1. — Gazella cf. capricornis (Wagner, 1848) from Akkaşdağı, skull AKB-29; A, lateral view; B, ventral view. Scale bar: 5 cm.

FIG. 2. — Gazella cf. capricornis (Wagner, 1848) from Akkaşdağı; A, skull AK2-443, lateral view; B, skull AK5-598, ventral view. Scale bar: 5 cm.

FIG. 3. — Gazella cf. capricornis (Wagner, 1848) from Akkaşdağı, frontlet AK12-72; A, lateral view; B, frontal view. Scale bar: 5 cm.

FIG. 5. — Gazella from Akkaşdağı, mandibles, labial view; A, G. aff. pilgrimi Bohlin, 1935, AK5-256; B, G. cf. capricornis (Wagner, 1848), AK3-189. Scale bar: 4 cm.