Gazella aff. pilgrimi Bohlin, 1935

Kostopoulos, Dimitris S., 2005, The Bovidae (Mammalia, Artiodactyla) from the late Miocene of Akkaşdağı, Turkey, Geodiversitas 27 (4), pp. 747-791 : 751-755

Gazella aff. pilgrimi Bohlin, 1935

DESCRIPTION

Despite the great variability observed in the predominant Gazella cf. capricornis from Akkaşdagwı, several specimens with clear gazelline morphology are placed out of the suggested limits (either morphologically or dimensionally), indicating the presence of a second, badly documented Gazella species. Three specimens can be certainly placed in this form: the frontlet AK5-601 ( Fig. 4 ) and the horn-cores AK5-642 and GOK-184.

In contrast to the previous gazelle, the horn-cores of this form are more closely situated at the base, longer (> 130 mm), less diverged and more tilted and curved backwards (52° in AK5-601) with a shorter pedicle, smaller and shallower postcor- nual groove and slightly larger mean size (Appendix: Table 5). They lack the deep longitudinal grooves on their surface and they appear more compressed mediolaterally, especially in their upper half (Appendix: Table 5). The index DT × 100/DAP varies between 75.1 and 84.5 at the base becoming smaller towards the top (Appendix: Table 5), indicating an opposite pattern comparatively to the described G. cf. capricornis .

Several other horn-core specimens (GOK-183, AKA-42, AKA-49, AKB-45) showing longer horn-cores, shorter pedicles and/or stronger mediolateral compression than in G. cf. capricornis , seem also to belong to this form.

A part of skull (AK2-442) and a mandibular ramus (AK5-256) can also provisionally be ascribed to them. The skull specimen AK2-442 preserves only the braincase and part of the frontals. The maximum width of the braincase is 64.6 mm versus 51.9-58.0 mm in G. cf. capricornis , indicating a slightly larger size (at about 25%). The teeth of the mandible AK5-256 ( Fig. 5A ) are slightly larger than that of Gazella cf. capricornis (length m1-m3: 40.6 mm in AK5-256) but of the same hypsodonty. The molars bear basal pillars and the second valley of p3 is rather open.

COMPARISON

Gazella is recorded in the Akkaşdagwı fauna by two unequally represented species of slightly different size. The predominant species is characterized by medium size, short premolar row, robust and relatively short horn-cores uprightly inserted on the cranial roof, moderately to strongly curved and divergent, well grooved with at least one deep posterocentral furrow and smoothly compressed mediolaterally. The second, less documented species presents a slightly larger size, a shorter pedicle and more tilted, longer and more compressed mediolaterally horn-cores.

More than one dozen of different Gazella species have been described from the late Miocene of Eurasia, leading to an extremely complex systematic and synonymy status, which resolution is, however, beyond the subjects of the present work. Both Akkaşdagwı gazelles differ by their larg- er size and horn-core setting and morphology from the small Vallesian species G. ancyrensis Tekkaya, 1973 from middle Sinap ( Turkey), G. gracile Korotkevitch, 1976 from Berislav ( Ukraine) and G. praegaudryi Arambourg, 1959 from Bou Hanifia ( Algeria) ( Tekkaya 1973a; Korotkevitsch 1976; Bouvrain 1996). Gazella lydekkeri Pilgrim, 1937 from Pakistan is also smaller with longer premolars, shorter, slenderer and remarkably less compressed horn-cores than the Akkaşdagwı gazelles. G. schlosseri Pavlow, 1913 from Grebeniki and adjacent territories ( Pavlow 1913; Korotkevitsch 1976) differs by its shorter, more rounded, deeply grooved and almost uncurved horn-cores with swelling anteroproximal face and flattened posterior one.

The systematic status of G. pilgrimi Bohlin, 1935 from Samos is quite complicated ( Bohlin 1939; Bouvrain 1996). The species is characterized by short pedicles, long horn-cores, strongly inclined backwards and moderately diverged with strong mediolateral compression and well grooved surface. These features resemble those of the second and less documented gazelle from Akkaşdagwı, which is, therefore, referred to Gazella aff. pilgrimi . Two types of posterior curvature can be seen in G. pilgrimi : weakly curved posterior face (the type specimen from Samos figured by Schlosser [1904: pl. XIII, fig. 1s; G. gaudryi of Arambourg F Piveteau [1929s; G. pilgrimi from PXM and RZO [ Bouvrain 1996 s) and strongly curved posterior face, especially in the distal part of the horn-core ( G. longicornis Andree, 1926 [pl. XVI, figs 3, 6s; G. longicornis from Ukraine [ Korotkevitsch 1976 s; G. capricornis of Solounias [1981: fig. 46s; G. pilgrimi from Vathylakkos [ Bouvrain 1996 s). Although the significance of this character is not clear (e.g., in the Ukrainian sample of G. longicornis intermediate types of the horn-core’s curvature are present; Korotkevitsch 1976: pls XIV-XVIII), the second gazelle from Akkaşdagwı approaches the “curved type ”.

The general morphological and proportional characters of the predominant gazelle from Akkaşdagwı recall those of G. mytilinii Pilgrim, 1926 , G. capricornis (Wagner, 1848) and G. deperdita (Gervais, 1847) . The characters used by Solounias (1981) to differentiate G. mytilinii from G. capricornis seem unreliable as they are mostly referred to G. pilgrimi (synonym of G. capricornis according to Solounias 1981). G. mytilinii is a little known species, recorded from Samos island ( Greece; Solounias 1981). It shares with some specimens referred to G. capricornis (such as the specimen figured by Gaudry [1862 -1867: pl. LVI, fig. 1s as G. brevicornis Roth F Wagner, 1854 and the Pikermi skull BMNH M13005 mentioned by Pilgrim F Hopwood [1928s), the relatively more uprightly inserted horn-cores with medium curvature and compression, the similar basioccipital structure, and the similar premolar/molar ratio. It is quite interesting that the skull specimen M13005 stored in BMNH differs from the second available Pikermi Gazella skull M 11440 in having higher occiput, shorter and more inflated opisthocranium, shorter basioccipital, stronger basioccipital-palate angle and more uprightly inserted and less laterally diverged horn-cores with more circular cross-section especially toward the apexes ( Fig. 6 ). This set of characters has been seen on the type specimen of G. mytilinii NHMW A 4777 and the probably conspecific AMNH 20706 from Q1 of Samos. We should therefore admit that the variation limits of the Pikermian G. capricornis are wide enough to include the “morphotypes” of G. mytilinii and M13005 or that a second nameless species occurs at Pikermi but such a revision is also beyond the purposes of the present work.

G. capricornis shares several morphological characters and presents a great dimensional overlap with G. deperdita from Cucuron and Mont Lubéron ( France), allowing some authors to regard them as conspecific or local races of the same species. G. capricornis differs, however, from G. deperdita in the slightly larger size, relatively longer and more uprightly inserted horncores with lesser degree of posterior curvature and weaker mediolateral compression ( Fig. 7 ; Appendix: Table 6). Moreover, the toothrow of G. capricornis is smaller than that of G. deperdita but with more elongated premolar row (Appendix: Table 6). The p4 of G. capricornis is elongated (Appendix: Table 6) with usually free metaconid instead of short with usually closed talonid in G. deperdita ( Heintz 1971; Roussiakis 1996).

Concerning the horn-core structure ( Fig. 7 ), the p4 proportions and the toothrow length, the main gazelle from Akkaşdagwı approaches better the Pikermian species, and especially the “ M11440 morphotype”. Nevertheless, the posterolingual wall of p4 appears closed in the Akkaşdagwı gazelle and the premolar/molar ratio are significantly smaller than in the typical sample of G. capricornis . Such a short premolar row occurs however, in some populations of Gazella capricornis from Ukraine ( Korotkevitsch 1976). Skull comparison between the specimens M13005 and M11440 (BMNH) and PIK 2001 (MNHN) of G. capricornis from Pikermi and AKB-29, AK5-598 shows that the Akkaşdagwı form has slightly wider and more elongated opisthocranium (W of bimastoid = 52-56 in G. capricornis versus 57.6-59.5 in the Akkaşdagw ı form; L of the posterior face of the horn-core to nuchal crest = 62-75 in G. capricornis versus 78.4 in AKB-29). Finally, according to the poor available data the hypsodonty seems more advanced in the Akkaşdagw ı form than in the typical sample of G. capricornis (92 versus 72 for m2 [one specimen respectivelys and 78 versus 71 for m3 [two and one specimens respectivelys).

Judging from the comparison, the Akkaşdagwı gazelle seems to approach G. capricornis from Pikermi. A direct attribution to this species seems however difficult because of the shorter premolar row and the apparently more advanced hypsodonty observed in Akkaşdagwı and the possible presence of another gazelle species in the Pikermian sample, increasing taxonomic vulnerability. Therefore, I suggest referring the main gazelle at Akkaşdagwı to Gazella cf. capricornis .

Turkish gazelles are well known from several late Miocene localities but species determination is usually obscure. The gazelle from KTD is significantly smaller than the Akkaşdagw ı forms and close to G. gracile from Berislav (see also Bouvrain 1994a). A similar horn-core pattern also occurs in Garkın and Mahmutgazi (Type III and part of Type II and IVa of Köhler 1987) that could be equally related to G. ancyrensis from Middle Sinap. The gazelle from Kayadibi (Type I of Köhler 1987) forms a well distinct sample from the rest of Turkish gazelles, including the Akkaşdagwı ones. This form is characterized by straight and rounded horn-cores of larger size than in the previous group and in accordance with Köhler (1987) I consider it as probably belonging to G. schlosseri . The horncore morphology and proportions and the short premolar row of the Kemiklitepe A-B gazelle ( Bouvrain 1994a) indicate close relations with the predominant gazelle from Akkaşdagwı. Anyway, the Kemiklitepe A-B material includes some horn-core specimens with slightly different proportions (KTA-149, KTB-79), which could suggest the presence of a second species. Specimens similar to the main Akkaşdagwı form can also be found at Mahmutgazi, Kınık (part of Type IVa and b of Köhler 1987) and Çoban Pınar (sp. 1917 MTA-MA). The skull specimen SaG 7-5/45 from Garkın, attributed by Köhler (1987: fig.74) to her Type II, as well as some other specimens ascribed to the same form ( Köhler 1987: pl. VIII, fig. 3), seem quite distinct from the rest of the Garkın material and Akkaşdagwı either. Their morphology and horncore proportions rather approach those of G. “ mytilinii ” from Samos. The gazelle from Küçükyozgat ( Şenyürek 1953) resembles G. aff. pilgrimi from Akkaşdagwı and G. pilgrimi from Axios valley ( Bouvrain 1996). A single available specimen from Kavakdere (sp. 2276-AAK/26, MTA-MA) is significantly larger than that of the Akkaşdagwı gazelles, indicating similarities with the specimen BMNH M5420 from Samos and RZO-159, 160, for which Bouvrain (1996) suggests the creation of a new taxon outside of Gazella .

Figures

FIG. 4. — Gazella aff. pilgrimi Bohlin, 1935 from Akkaşdağı, frontlet AK5-601, lateral 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.

FIG. 6. — Drawings of Pikermian Gazella; A, C, BMNH M11440; B, D, BMNH M13005; A, B, cranium in lateral view; C, D, basioccipital in ventral view. Scale bar: 2 cm.

FIG. 7. — Size distribution of Gazella horn-core, measurements at the base (A) and at 7 cm above the base (B). ■, G. cf. capricornis (Wagner, 1848), Akkaşdağı;, G. capricornis, Pikermi; +, G. deperdita (Gervais, 1847), Lubéron/Cucuron (France). Abbreviations: DAP, anteroposterior diameter; DT, transverse diameter.