Geniohyidae ANDREWS , 1906

Al-Kindi, Mohammed, Pickford, Martin, Al-Sinani, Yusouf, Al-Ismaili, Ibrahim, Hartman, Axel & Heward, Alan, 2017, Large Mammals From The Rupelian Of Oman - Recent Finds, Fossil Imprint 73 (3 - 4), pp. 300-321 : 305

Family Geniohyidae ANDREWS, 1906

Genus cf. Bunohyrax SCHLOSSER, 1910

M a t e r i a l. Isolated m/3 fragment (currently without accession number).

D e s c r i p t i o n. A left m/3 fragment of a large hyracoid was found in the Ashawq Formation by the Thomas Expedition, but was never described. The specimen preserves a small part of the protoconid, the rear half of the metaconid, the complete entoconid, part of the hypoconulid, and the lingual half of the hypoconid ( Text-fig. 9 ). The tooth would originally have been about 25.3 mm long by about 14.6 mm broad at the second lophid.

The entoconid has a pre-entocristid that leads mesially into the median transverse valley, separated at its termination from the end of the pre-hypocristid. The latter cristid is directed mesio-lingually from the apex of the hypoconid, and ends in the midline of the tooth. The entoconid has a second cristid reaching buccally towards the hypoconid, where it joins a short cristid leading lingually from the apex of the hypoconid. The post-entocristid is short and directed distally. There is a short cristid in the bucco-distal corner of the entoconid, which joins the post-hypocristid, closing off a shallow foveid between the entoconid and hypoconid. The pre-hypoconulid cristid reaches towards the end of the post-hypocristid, ending at its base. The enamel in the floor of the valley between the hypoconulid and the entoconid is coarsely wrinkled, whereas that covering the mesial walls of the metaconid and entoconid is lightly wrinkled. The mesial walls of the tooth are almost vertical.

D i s c u s s i o n. Among Hyracoidea , the tooth is morphologically closest to members of the family Geniohyidae , Geniohyus ANDREWS, 1904 and Bunohyrax SCHLOSSER, 1910 . In particular, the presence of four cristids in the entoconid, the presence of a fovea between the hypoconid and entoconid, and the wrinkled enamel all fit with members of this family. The steepness of the lingual wall of the crown pleads for affinities with Bunohyrax rather than with Geniohyus . The latter genus has sloping, slightly convex, lingual walls in the lower molars.

The Ashawq specimen is considerably smaller than Geniohyus adiposum (FORSTER- COOPER, 1924) from Bugti, Pakistan ( Pickford 1986b). It has comparable dimensions to the Fayum, Egypt, species Geniohyus mirus ANDREWS, 1904 ( Matsumoto 1926) , Bunohyrax fajumensis ANDREWS, 1904 , and Bunohyrax affinis MATSUMOTO, 1926 (the latter is likely a synonym of Bunohyrax fajumensis ). Pickford (1986a) described a similar specimen from Malembe (5°19’S: 12°01’E) in Angola.

Pickford et al. (1994) listed three hyracoid taxa from Thaytiniti: an unidentified medium-sized species based on some upper molar fragments, and two small species, cf. Saghatherium bowni RASMUSSEN et SIMONS, 1991 , and cf. Thyrohyrax meyeri RASMUSSEN et SIMONS, 1991 , based on isolated teeth. The specimen described above could well represent the same taxon as the unidentified upper molar fragments from Thaytiniti.

The same authors listed two species of hyracoids from Taqah, east of Salalah: a medium-sized species similar to an un-named species from Quarry L 41 in the Fayum, Egypt, and a smaller species, Thyrohyrax meyeri , also known at Quarry L41.

Figures

Text-fig. 9. Fragmentary left m/3 with reconstructed outline of a bunodont hyracoid from the Ashawq Formation. a) lingual view, b) stereo occlusal view (scale bar 10 mm).