Ouranopithecus turkae, GüLeç & Sevim & Pehlevan & Kaya, 2007

Güleç, Erksin Savaş, Sevim, Ayla, Pehlevan, Cesur & Kaya, Ferhat, 2007, A new great ape from the late Miocene of Turkey, Anthropological Science 115 (2), pp. 153-158 : 154-157

Species Ouranopithecus turkae sp. nov.

Ovibovini indet.

Bovidae gen. et. sp. indet .

Etymology. Turkae for the people who live in Anatolia.

PERISSODACTYLA

Rhinocerotidae

Holotype. CO-205, a maxilla fragment with right C–M2 and left I1 –M3.

Chilotherium sp .

Rhinocerotinae indet .

Ceratotherium neumayri

Paratypes. CO-300, a subadult mandible with right C–M2 and left P3–M1; CO-710, an adult partial right mandible with P3–M2; holotype and paratypes are housed at the University of Ankara .

Equidae

Hipparion sp. A

Hipparion sp. B

Hipparion sp. C

PROBOSCIDEA

Diagnosis. O. turkae is distinguished from other Miocene hominoids, including Ankarapithecus as well as the probable sister taxon Ouranopithecus macedoniensis, by a constellation of dentognathic features that includes short- er and more vertical premaxilla, palate narrow relative to postcanine occlusal size, and homomorphic P3 and P4. The P3 is nearly symmetrical and oval in occlusal outline and the pre-and postparacrista are subequal in length. O. turkae is further distinguished from O. macedoniensis by its smaller relative canine to cheek tooth size proportions, shorter-crowned male canines, maxillary incisors nearly aligned with the canines, and perhaps larger (male) size.

Gomphotheriidae

Choerolophodon pentelici

Description

The upper incisors are very heteromorphic in size and shape. The I1 is robust and squat, with nearly equivalent me-

siodistal and labiolingual dimensions ( Table 2). Its lingual surface is marked by deep vertical fissures, including prominent mesial and distal lingual grooves. The worn incisal edge angles steeply lingually. A prominent basal tubercle, contributing to the labiolingually thick crown, is slightly worn along the incisal wear plane. The I2 crown is wider labiolingually than mesiodistally, and has a strong basal lingual cingulum and marked lingual relief. Relative to the cheek teeth, the incisors are small.

In buccal aspect, the upper canine crown shoulders are set near the crown base. The basal canine outline is a labiolingually elongate oval. The mesial groove is narrow and deep. The right canine tip was fractured antemortem and the dentine was slightly worn apically. There is a distolingual honing facet formed by contact with the P3 and an extensive and mammelated lingual cingulum. Relative to postcanine tooth size, CO-205 has among the smallest canines of presumed males of any known late Neogene hominoid ( Figure 3 ).

The O. turkae upper postcanine teeth are in the size range of living gorillas. However, they feature broad, low, rounded cusps, weak cristae, broad, shallow occlusal basins, and simple occlusal morphology. The summed postcanine occlusal area of the CO-205 exceeds that of all other Miocene hominoid primate taxa except Gigantopithecus .

Except for P3, O. turkae molars and premolars lack cingula and their enamel is thick. The enamel thickness of the lateral crown faces in CO-300 measured by recently standardized micro-CT methodology ( Suwa and Kono, 2005) at the major cusps ranges from 1.81 to 2.35 mm in the M2

( Figure 4 ) and from 1.55+ to 2.03+ mm in the M1. Average enamel thickness in the mesial cusp section of the little-worn M2 is 1.94 mm. The relative enamel thickness value (enamel area divided by square root of dentine area; Smith et al., 2003, 2004; Kono, 2004) of M2 is 27.3, making this the thickest enameled Miocene hominoid molar yet examined based on these parameters ( Smith et al., 2003, 2004).

The O. turkae P3 is oval, rather than of an asymmetrical triangular form as seen in most other fossil and modern apes. The P3 protocone and paracone are of subequal size. In buccal aspect, the crown profile also lacks the asymmetry seen in other ape P3s. This is because of the absence of a strong rootward mesiobuccal projection of the enamel line, and because the distobuccal (postparacrista) and mesiobuccal (preparacrista) occlusal edges are nearly equal in length. The P4 crown is also more oval and symmetric than in most other apes. The mesial and distal foveae of both upper premolars are bounded by thick marginal ridges.

In keeping with the large and robust premolars, the upper molars are massive, with distal cusps well expressed and not reduced as in some Miocene hominoids. The M1 is smaller than the M2, which is slightly smaller than M3. The latter tapers distally, is mesiodistally elongate, and bears accessory distal cusps. The M1 cusps were worn low before enamel perforation, with dentine exposed only at the protocone. The enamel thickness of the upper molars was not measured, but the enamel bounding the exposed dentine suggests a thickness comparable to that of the measured lower molars.

Only the roots and alveoli of the mandibular incisor are preserved in CO-300. The erupting canine had not reached occlusion, but it is tall, narrow, and pointed. In keeping with the morphology of the upper premolars, the P3 is more oval in occlusal outline than in most apes and even some early hominids. A thin lingual cingulum is present. The protoconid is sharp and prominent. A small honing facet can be seen on the mesio-buccal face of the right P3. The P3 of CO- 710 has a prominent wear facet from protoconid to metaconid and also has a slight honing facet on the mesiobuccal surface. As is the case for the P3, O. turkae has slightly more oval P3s than those of O. macedoniensis.

As in the P3, in buccal view, the mesial occlusal edge (preprotocristid) of the P3 in CO-300 is subequal (but slightly longer) in length compared to the distal occlusal edge (postprotocristid). This morphology is unlike the distinctly longer preprotocristid of most other Miocene and modern apes. Hence, the O. turkae P3 is rather less sectorial in shape than in most other known Miocene hominoids, resembling the modern chimpanzee in this respect. The mandibular dental dimensions are given in Table 3.

The palate of CO-205 is distorted, but judging from the posterior margins of the incisor and canine alveoli, as well as a fragment of bone along the right lateral edge of the nasal aperture, it featured a short and fairly vertical premaxilla. As the incisors and canines are relatively reduced, the anterior palate is presumed to be relatively narrow, whereas the massive postcanine teeth render the entire palate long and seemingly narrow relative to postcanine size and palatal length. The incisors extend minimally beyond the anterior transverse plane of the canines and are notably vertically implant- ed, particularly for a young adult. There was little or no precanine diastema. The maxillary palatine processes are thin. We consider O. turkae to have had a more vertical face than O. macedoniensis. These apparently derived features may relate to the younger age of the Turkish fossils.

Discussion

O. turkae is most similar to Ouranopithecus among known Miocene hominoids. The two taxa share many derived features, such as the weakly asymmetric upper and lower P3s, absolutely and relatively large postcanine size, and hyper-thick molar enamel, probably related to a diet that required heavy mastication. This is also evidenced by instances of heavy wear in upper (RPL-128, XIR-1) and lower (RPL-56) dentitions of this genus. This wear was probably associated with an adaptation to more open habitats than those of extant apes. Indeed, Ouranopithecus lived in Eurasia during a time of considerable decline in forest cover, and development of more open country and seasonable environments ( Bernor, 1983; de Bonis et al., 1994; Bernor et al., 1996; de Bonis and Koufos, 1999; Begun and Kordos, 1997; Begun, 2005).

Previous interpretations of Ouranopithecus had suggested that this genus was a plausible ancestor of African Pliocene Australopithecus based on dentognathic morphological similarities ( Begun et al., 2003). Indeed, the resemblance of the upper premolars of O. turkae and non-robust Pliocene Australopithecus such as Au. africanus, is striking. However, most early Australopithecus dentitions, A. anamensis ( Ward et al., 2001) and A. afarensis ( White, 1977), actually have more primitive postcanine dental features than seen in Ouranopithecus . Furthermore, the African late Miocene hominids Orrorin ( Senut et al., 2001) , Ardipithecus ( White et al., 1994; Haile-Selassie, 2001; Haile-Selassie et al., 2004), and Sahelanthropus ( Brunet et al., 2002) lack dentognathic specializations associated with tough/abrasive diets such as that inferred for Ouranopithecus and in early Australopithecus . Such considerations lead us to interpret Ouranopithecus as manifesting substantial dentognathic parallelism with Australopithecus ( Begun and Kordos, 1997; Begun, 2001). Hence, we do not consider these features of Ouranopithecus to indicate placement within the hominid (African ape-human) clade (contra de Bonis et al., 1990, 1999; de Bonis and Koufos, 1993, 1994, 1997; Koufos, 1993).

O. turkae , the youngest and largest of known Turkish Miocene hominoids, is unlike all modern and other fossil great apes in what is known of its preserved anatomy and its environmental circumstances.

Figures

Figure 3. The Valles-Penedes Dryopithecus laietanus IPMC 18000-5 (left) and Corakyerler CO-205 (right). IPMC 18000-5 is mirrored to facilitate comparisons (from Moyà Solà and Köhler, 1995).

Figure 4. Radial enamel thickness of the lateral crown face at each of the five major cusps measured by microfocal X-ray CT. Right, occlusal view surface rendered image of the M2 (CO-300) with white line indicating position of the mesial cusp section (section running through the protoconid and metaconid dentine cusp tips); left, corresponding grayscale image of the mesial cusp section; white bar indicates 2 mm. Maximum lateral enamel thickness in the little-worn lower M2 mesial cusp section (Suwa and Kono, 2005) was 2.35 mm in the protoconid and 2.08 mm in the metaconid. The three-dimensional radial lateral enamel thickness ranged from 2.26 to 2.31 opposite the buccal M2 main cusps and 1.81 to 2.15 opposite the lingual M2 main cusps. In the right M1 with flattened buccal cusps, the maximum lateral enamel thickness in the mesial cusp section was 1.55+ in the protoconid and 1.73 in the metaconid. The three-dimensional radial lateral enamel thickness ranged from 1.63+ to 2.03+ opposite the buccal M1 main cusps, and 1.68 to 1.73 opposite the lingual M1 main cusps. Scans were taken at 150 micron pixel resolution for the mandibular canine through M1, and at 40 micron pixel resolution for the mandibular M2