Hyainailouros cf. napakensis Ginsburg, 1980

Morlo, Michael, Friscia, Anthony, Miller, Ellen R., Locke, Ellis & Nengo, Isaiah, 2021, Systematics and paleobiology of Carnivora and Hyaenodonta from the lower Miocene of Buluk, Kenya, Acta Palaeontologica Polonica 66 (2), pp. 465-484 : 469

Hyainailouros cf. napakensis Ginsburg, 1980

Fig. 2G , Table 1.

Material.—KNM­WS 12622, right lower canine fragment, with the tip and root broken; from Buluk, east of Lake Turkana, Kenya; lower section of the Buluk Member, Bakate Formation, uppermost lower Miocene.

Description.—The canine fragment KNM­WS 12622 ( Fig. 2G ) bears a serrated crest running from the point where the tip is broken to the inferior enamel border. Posterior to this crest, a groove is present, which runs vertically from the base towards the tip. Mesially, the enamel­dentine juncture curves up towards the tip of the tooth, which is a typical feature of hyaenodonts. A vertical attrition facet is present. In all these features, the tooth resembles the lower canines of H. sulzeri ( Ginsburg 1980) and S. kutokaafrika ( Borths and Stevens 2019) , but KNM­WS 12622 is smaller than the canines in either of these two taxa. The Buluk specimen is also narrower buccolingually than would be expected for an amphicyonid, and shorter antero­posteriorly than would be expected for an early Miocene felid. The Buluk canine fragment is also too large to belong to any species of Anasinopa Savage, 1965 , the second largest hyainailourid from Rusinga Island, Kenya, after Hyainailouros ( Morales and Pickford 2017) . We thus assign the tooth to H. cf. napakensis , as the smallest known species of Hyainailouros . The assignment of an isolated canine at the species level, however, can only be tentative.

Remarks.—The partial canine KNM­WS 12622 is the only specimen that suggests a second, smaller species of Hyainailouros may be present at Buluk. The tooth presents a typical hyainailourid morphology but is much smaller than in H. sulzeri . The occurrence of a second and smaller species of Hyainailouros at Buluk is not considered surprising, as the co­occurrence of two species of Hyainailouros , one large and one small has been documented previously in the Kenyan lower Miocene ( Lewis and Morlo 2010; Friscia et al. 2020), mostly involving H. nyanzae , a species recently synonymized with H. napakensis ( Morales and Pickford 2017) .

Figures

Fig. 2. Hyaenodonts Hyainailouros sulzeri Biedermann, 1863 (A–F) and Hyainailouros cf. napakensis (G), from the lower Miocene of Buluk, Kenya. A. KNM­WS 12624, isolated right P1 in buccal (A1), lingual (A2), and occlusal (A3) views. B. KNM­WS 12626, isolated left P2 in buccal (B1), lingual B2), and occlusal (B3) views. C. KNM­WS 12628, posterior fragment of a right P3 in occlusal view. D. KNM­WS 12662, isolated left P4 in buccal D1), lingual (D2), and occlusal (D3) views, notice size difference between P3 and P4 and different shape of lingual cingulum indicated by the arrow. E. KNM­WS 65874, isolated left p3 in in buccal (E1), lingual (E2), and occlusal (E3) views. F. KNM­WS 12627, proximal left femur in anterior view, notice low condyle, indicated by the arrow, being about as high as femoral head. G. KNM­WS 12622, right lower canine in buccal (G1), posterior (G2), and mesial (G3) views, notice basal enamel border, indicated by the arrow, concave towards the tip of the tooth.