Hyainailouros sulzeri Biedermann, 1863

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 : 467-469

Hyainailouros sulzeri Biedermann, 1863

Fig. 2A–N , Table 1.

For synonymy list see Morales and Pickford (2017).

Holotype: NWSW, left maxilla with I3, C, P2–M1, and right mandible with c, p4, m2–m3.

Type locality: Veltheim, Switzerland ( Biedermann 1863: pls. 4, 5; Helbing 1925: figs. 7–11, pl. 6; Beaumont 1970: figs. 1, 2; Ginsburg 1980: figs. 1, 2).

Type horizon: Middle Miocene (MN 6).

Material.—KNM­WS 12624, right maxillary fragment with P1; KNM­WS 12626, partial left P2; KNM­WS 12628, posterior fragment of a right P3; KNM­WS 12662, left P4; KNM­WS 12627, proximal left femur; KNM­WS 12620, distal part of a metatarsal III or IV; KNM­WS 65874, left p3. All from Buluk, east of Lake Turkana, Kenya; lower section of the Buluk Member, Bakate Formation, uppermost lower Miocene.

Description.—The right P1 preserved in KNM­WS 12624 ( Fig. 2A ) is unicuspid with the paracone located centrally. The preparacrista curves strongly lingually and ends at the antero­lingual corner of the tooth. The postparacrista is positioned centrally and terminates at the most posterior point of the tooth. The specimen lacks a cingulum. A facet indicating horizontal abrasion is visible on the lingual aspect of the tooth, between the paracone and the tooth base.

The isolated left P2 KNM­WS 12626 ( Fig. 2B ) resembles P1 but is slightly larger. As in P1, the unicuspid tooth has a lingually curving preparacrista, a centrally running postparacrista, and lacks a cingulum. The posterior end of the postparacrista is obscured by breakage. The paracone has an abrasion facet.

KNM­WS 12628 ( Fig. 2C ) is a right, posterior fragment of a premolar, which we identify as a P3 because it has a straight cingulum rather than a curved cingulum as would be typical of a P4 (see the P4 of KNM­WS 12662 of Hyainailouros sulzeri and Simbakubwa kutokaafrika Borths and Stevens, 2019 ). In H. napakensis and H. ostheolastes , the lingual cingulum of P4 is also more curved than in KNM­WS 12628. Moreover, the metastyle of KNM­WS 12628 is clearly shorter than that of KNM­WS 12662. We thus interpret this fragment as a P3.

The P4 KNM­WS 12662 ( Fig. 2D ) is slightly larger than the P 4 in the holotypes of S. kutokaafrika and H. sulzeri , but the Buluk specimen shares the high P4 length/width index present in these two taxa. The Buluk P4 also resembles other specimens of H. sulzeri ( Helbing 1925; Ginsburg 1980: fig. 3), in exhibiting a characteristic symmetry, produced by having the parastyle nearly as long as the metastyle. In S. kutokaafrika the parastyle is less pronounced. The metastyle in KNM­WS 12662 is separated from the paracone by a deep notch, and the short protocone is located directly below the paracone. The protocone in H. ostheolastes and H. napakensis is longer than that in H. sulzeri . A strong cingulum surrounds the tooth. The dental enamel is rugose with small horizontal striations.

The isolated left p3 KNM­WS 65874 ( Fig. 2E ) is low crowned, unicuspid, and surrounded by a strong cingulid, which curves slightly lingually directly lingual to the paraconid.

The proximal left femur KNM­WS 12627 ( Fig. 2F ) resembles, and is similar in size to, a femur of H. sulzeri known from Europe ( Ginsburg 1980: fig. 33). In particular, the size and placement of the third trochanter on KNM­WS 12627 is identical to that in the European specimen, and the proximal end, in both the Buluk and European specimens, resembles Amphicyon major (Blainville, 1841) (see Argot 2010: fig. 8E) in having the greater trochanter only slightly lower than the femoral head. In addition, the overall size of KNM­WS 12627 suggests that it represents an animal larger than a lion, which places the Buluk specimen in a size class exceeding what would be expected for even the very large species of Cynelos from Buluk.

KNM­WS 12620 preserves the distal part of metatarsal III or IV, and the specimen resembles the metatarsals of European H. sulzeri . The Buluk metatarsal has a width of 27.3 mm, which more closely approximates the size of metatarsal III than metatarsal IV (see Ginsburg 1980: fig. 42), and KNM­WS 12620 is also much larger than what would be expected for either African species of Amphicyon Lartet in Michelin, 1836 ( Morales et al. 2003) or the very large species of Cynelos from Buluk.

Remarks.—Specimens from Buluk attributed to H. sulzeri are directly comparable to the European holotype material in both size and morphology (see Ginsburg 1980: fig. 1). In particular, the P4 from Buluk, KNM­WS 12662, resembles H. sulzeri and differs from S. kutokaafrika ( Borths and Stevens 2019: fig 6) in having a stronger parastyle, longer metastyle, and a narrower paracone. The P3 fragment, KNM­WS 12628, is also reminiscent of the H. sulzeri type material, but it is possible that KNM­WS 12628 represents a P4 of H. napakensis . This alternative interpretation is less likely, because the metastyle in the Buluk specimen seems to be less well developed than in H. napakensis , and the lingual cingulum is less curved (see Borths and Stevens 2019: fig. 6B). The postcranial remains are attributed to H. sulzeri on the basis of their similarity to European specimens of this species, and because their size exceeds that of African Amphicyon and Cynelos from Buluk.

The Buluk material of H. sulzeri further documents the broad geographic range of this genus in Africa ( Morlo et al. 2007; Lewis and Morlo 2010; Morales and Pickford 2017), especially if the North African “ Megistotherium ” osteothlastes is regarded as Hyainailouros osteothlastes (after Morlo et al. 2007 and Morales and Pickford 2017). The P4 parastyle of the Buluk specimen is as long as it is in Simbakubwa . P4 parastyle length, however, differs intra­ and interspecifically within the species of Hyainailouros , and it may be large or small in H. sulzeri (see Ginsburg 1980: figs. 3, 4). The P4 parastyle is also large in H. “ fourtaui ” ( Morlo et al. 2007, = H. osteothlastes after Morales and Pickford 2017) from Moghra, Egypt, while it is short in both the holotype of H. ostheolastes and in H. napakensis . As all other large hyaenodontid specimens from Buluk can be assigned to H. sulzeri , we also assign the P4 to this species. As for a possibly varying orientation of the protocone in the upper molars, the Buluk material provides no new information.

Stratigraphic and geographic range.—Lower to middle Miocene of Europe and Africa ( Lewis and Morlo 2010).

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.