Sivaonyx hessicus (Lydekker, 1890)

Peigné, Stéphane, 2016, Carnivora, Geodiversitas 38 (2), pp. 197-224 : 200-202

Sivaonyx hessicus (Lydekker, 1890)

( Fig. 1 C-E; Table 1)

Lutra sp. – Malik & Nafiz 1933: 32, 66, 109. — Yalçınlar 1954: 112. — Ozansoy 1957: 33.

REFERRED MATERIAL FROM KÜÇÜKÇEKMECE. — KÇ 83, fragment of right hemimandible with m1.

DESCRIPTION

A small portion of the dentary is preserved ( Fig. 1 C-E); at the level of the carnassial it is thick and deeper than the length of the m1.

The carnassial is typical of lutrines. It is robust, elongated though low and wide. The trigonid cuspids are low and of approximately equal height; the metaconid is strong and slightly distal to the protoconid; the paraconid is large, triangular in occlusal shape, and occupies nearly the entire mesial half of the trigonid; its distal face is transversely oriented. A prominent crest (= protoconulid, in Morales & Pickford 2005; = postprotoconid cusplet, in Pickford 2007) is present at the distal base of the protoconid; faint notches separate this crest from the protoconid and the hypoconid crest of the talonid. The trigonid basin is deep and opened lingually so that the paraconid and metaconid are deeply separated. A strong cingulid is present on the labial side of the crown and on the lingual side of the paraconid. The talonid is wide and rounded, with a shallow basin; the hypoconid crest is wide (the lingual slope occupies one-half of the talonid width) and tall relative to the lingual ridge. The hypoconid is poorly individualized, but is slightly prominent relative to the distal rim of the talonid. The tooth has its maximum width approximately at the trigonid/ talonid boundary.

COMPARISONS AND DISCUSSION

The generic assignment of the material is based on a comparison with most of the late Miocene and Pliocene species of lutrines. Besides the robustness of the dentary, which is hard to estimate here, species of Sivaonyx are characterized by “an m1 with a low trigonid with cuspids of approximately equal height, deeply separated paraconid and metaconid, a talonid wider than the trigonid, a large hypoconid crest, a shallow talonid basin, a low but distinct entoconid crest, a cingulid marked on the labial side that may extend on to the lingual side of the paraconid” ( Peigné et al. 2008: 795). These features are present in KÇ 83. An additional diagnostic feature of the species of Sivaonyx mentioned by Pickford (2007) is mandibular depth greater than m1 length, which is also observed in KÇ 83, but this may also be the case in non-bunodont otters such as Lutra spp. (personal observations). The specimen from Küçükçekmece differs from Vishnuonyx Pilgrim, 1932 (and extant genera such as Lutra Brisson, 1762 ) in having an m1 that is more bunodont and with a lower trigonid relative to the talonid, and from more bunodont taxa (e.g., Enhydriodon Falconer, 1868 , Djourabus Peigné et al. 2008 ) in having an m1 that is less bunodont and a more slender dentary. Many species of Sivaonyx have been described, especially from Africa and southern Asia ( Morales & Pickford 2005; Pickford 2007; Peigné et al. 2008; Werdelin & Peigné 2010). Most of these species have an m1 with a wider talonid and, generally, a larger size than the specimen from Turkey described here ( Table 1). In addition, according to Pickford (2007), S. gandakasensis Pickford, 2007 has also a shorter trigonid (57-64%) than in S. hessicus .

The specific assignment is based on a comparison with the holotype and single specimen of the European species originally described as Lutra hessica, BMNH 27486. This specimen is a fragment of right hemimandible with a fragment of p4 and m1 from the German locality of Eppelsheim (MN9, late Miocene). The geographic and stratigraphic proximity of the specimens of Eppelsheim and Küçükçekmece, in addition to their morphological similarity, support their assignment to the same species. Additional material is required to confirm this hypothesis. Because the specimen from Eppelsheim displays the diagnostic features of the genus Sivaonyx mentioned above, I propose to name this species Sivaonyx hessicus , an hypothesis already suggested by Morales & Pickford (2005) and, especially, by Pickford (2007). As noted by Pickford (2007), however, there is not much difference between Sivaonyx hessicus and the type species of the genus, S. bathygnathus . The species from Germany and Turkey may prove to be synonymous with this Asiatic species when more material is known. In his review of the Pliocene and Quaternary European otters, Willemsen (1992) concluded that the morphology of the m1of Lutra hessica suggested a closer relationship to Lutrini (i.e. Lutra , Lutrogale Gray, 1865 , Pteronura Gray, 1837 and their fossil relatives; see Willemsen 1992: 114), but his comparison was biased since he did not compare Lutra hessica with the species of Sivaonyx , of which many species have been described since then.

Figures

FIG. 1. — A, B, Indarctos arctoides (Depéret, 1895): MNHN.F.TRQ947, subcomplete left hemimandible with p4-m2 in labial (A) and occlusal (B) views; C-E, Sivaonyx hessicus (Lydekker, 1890): KÇ 83, fragment of right hemimandible with m1 in lingual (C), occlusal (D), and labial (E) views; F-H, Cryptophoca sp.: KÇ 101, fragment of left hemimandible in occlusal (F), lingual (G), and labial (H) views. Scale bars: 10 mm.