Dolichopithecus sp.

aff. Dolichopithecus sp.

Text-figs 4–6 L o c a l i t y. Milia.

M a t e r i a l. Ulna proximal left MIL 1779; tibia right

MIL 530.

D e s c r i p t i o n. The ulna retains only the proximal end and part of the diaphysis, slightly eroded, probably due to the action of water ( Text-figs 4, 5). The olecranon process and about half of the sigmoid notch (incisura semilunaris) are missing. The specimen is preserved in good condition and bears well-defined morphological features. The processus coronoideus is well-developed and pointed, the radial notch (incisura radialis) is well-defined and laterally rounded, followed by intense crista supinatoria. The tuberositas ulnae is slender, followed by a rather sharp margo volaris, and a hollow impression is formed between it and the crista supinatoria. In addition, a foramen nutricium can be seen near the margo volaris, and approximately in the middle of the shaft. On the posterior, the margo dorsalis is relatively thick and has a curvature at a height below the sigmoid notch ( Tab. 2).

( Text-fig. 6d, red arrow). The crista interossea is rounded. In the distal part, the sulcus malleoli tibiae is hollow, as well as the incisura fibularis. The malleolus tibiae is well developed with sub-triangular facies articularis malleoli. The facies articularis distalis tibiae is sub-square, whereas the facies articularis malleoli fibulae is semicircular and wide ( Text-fig. 6, Tab. 2). Overall, the inferior view shows the articular surface relatively trapezoidal ( Text-fig. 6f, red outline).

The tibia is almost complete and well preserved. Only the proximal part with the condylii, the eminentia intercondylica and the tuberositas tibiae are missing, whereas the margo infraarticularis is visible ( Text-fig. 6e). The diaphysis is rather long and slender. The anterior crista is thick and rounded, whereas linea poplitea is well distinguished up to the foramen nutricium in the upper third of the diaphysis

D i s c u s s i o n. The primate from Milia (MIL) is represented only by a few postcranial bones. A comparison of the ulna of Milia aff. Dolichopithecus sp. with that of Kryopigi Mesopithecus , apart from the dimensions, shows the following morphological characteristics: The coronoid process is more pointed ( Text-fig. 5, arrow 1), in the radial notch there is a clear incisura ( Text-fig. 5, arrow 2) between its medial and lateral circular-shaped articular facets ( Text-fig. 5, arrow 3). The crista supinatoria is more pronounced ( Text-fig. 5, arrow 4) and the impression deeper than that of the Mesopithecus ( Text-fig. 5, arrow 5). The dorsal margin is relatively thick and less flat, bearing curvature ( Text-fig. 5, arrow 6).

A specific feature of the ulna is the partial division of the radial incisure in two articular facets, one lateral (corresponding to some degree to the human radial notch) and one anterior, formed on the lateral surface of the coronoid process. The longitudinal ridge, which proximally reaches the lateral facet is strong, the depression posteriorly to it is shallower – not as deep and narrow as in Paradolichopithecus . At the same time the depression on the medial surface, posterior to the trochlear incisure is deep, similar to the condition in Dolichopithecus DEPÉRET, 1889 (see Delson 1973: fig. 59). The trochlear incisure (trochlear notch) is kidney-shaped, less broad than the one of Paradolichopithecus . Under the coronoid process the shaft expands proximally, though not as strongly as it does in Paradolichopithecus . The dimensions of the ulna MIL 1779 are relatively small in comparison with Paradolichopithecus , and also smaller than those of the known specimens of Dolichopithecus ruscinensis DEPÉRET, 1889 (see Szalay and Delson 1979: fig. 212).

Compared to male wild Papio cynocephalus (LINNAEUS, 1766) (RM 753, col. National Museum of Natural History, Sofia), the tibia from Milia is visibly shorter, but more robust and with a larger surface of the articular distal end. The distal articular end is wider medio-laterally, displaying a more rectangular shape, but not squarish one, as in Papio ( Text-fig. 6f). The shaft is slightly more curved in mediolateral view. The medial malleolus is shorter in comparison with Papio . In comparison with Paradolichopithecus , the lateral surface of the distal articular end in MIL 530 is less square, its malleolus is more ball-shaped, while in Paradolichopithecus , it bears a more flattened lateral surface. The bifurcated channel for the flexor muscle (see Sondaar et al. 2006) is barely noticeable, which may not be solely due to the mentioned bone erosion. These features, apart from showing taxonomic differences with Paradolichopithecus , also suggest a weaker terrestriality of the Milia tibia in comparison with Papio and Paradolichopithecus . Considering the morphology, as well as the dimensions, the geological age and the geographical location, we can assume that both ulna and tibia from Milia may both belong to Dolichopithecus balcanicus SPASSOV et GERAADS, 2007 , but this determination is for the moment only conjectural.