Elephas sp.

Suraprasit, Kantapon, Jaeger, Jean-Jacques, Chaimanee, Yaowalak, Chavasseau, Olivier, Yamee, Chotima, Tian, Pannipa & Panha, Somsak, 2016, The Middle Pleistocene vertebrate fauna from Khok Sung (Nakhon Ratchasima, Thailand): biochronological and paleobiogeographical implications, ZooKeys 613, pp. 1-157 : 16-17

Taxon classification Animalia Proboscidea Elephantidae

Elephas sp.

Referred material.

A fragmentary tusk, DMR-KS-05-03-22-1; a posterior fragment of a right lower molar, DMR-KS-05-03-17-12.

Material description.

Upper tusk: DMR-KS-05-03-22-1 is a short fragmentary tusk. The dorsal side is partially broken away (Fig. 9A, B). This tusk curves slightly upward and is dorsoventrally compressed and probably obovoid or oval in cross-section (Fig. 9B, C). The Schreger pattern in the dentine is poorly developed or absent. The fractures of the cross-section are developed, perpendicular to the outer surface ("radiate cracking or fracture pattern") ( van den Bergh 1999) (Fig. 9C). The maximum length of the preserved tusk is 196.1 mm and the mediolateral and dorsoventral diameters measured on the proximal cross-section are 71.3 and 49.1 mm, respectively.

Lower molar: DMR-KS-05-03-17-12 preserves only two adjoining worn plates of a high-crowned molar, distinctly more hypsodont than that of Stegodon (Tab. 4). The plates are thin, anteroposteriorly compressed, and closely spaced (Fig. 9D, E). The occlusal enamel loops or folds are small and thin, compared to Stegodon orientalis molars, single-layered, and almost irregular. The grinding surface of the anterior plate is buccally inclined (Fig. 9F), indicating this is a right molar.

Taxonomic remarks and comparisons.

The fragmentary tusk (DMR-KS-05-03-22-1) is distinguished from DMR-KS-05-03-15-2 ( Stegodon orientalis ) by a more rounded cross-section, a larger diameter, and a radiate fracture pattern with the development of concentric incremental lines (Fig. 9C). The outline of DMR-KS-05-03-22-1 resembles Elephas (e.g., Elephas maximus ( Palombo and Villa 2001) and Elephas celebensis ( van den Bergh 1999)). The lower molar is also congruent morphologically with Elephas ( Maglio 1973, Zhou and Zhang 1974), but differs from Palaeoloxodon namadicus in its thinner and smoother enamel ( Lydekker 1880, Zhou and Zhang 1974, Tshen 2013). We therefore assign these two specimens (fragmentary tusk and molar) to Elephas .