Rhinoceros unicornis Linnaeus, 1758

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 : 21-22

Taxon classification Animalia Perissodactyla Rhinocerotidae

Rhinoceros unicornis Linnaeus, 1758

Referred material.

A left mandible with p3-m3, DMR-KS-05-03-17-13; a left p2, DMR-KS-05-03-19-4; a right M1, KS-05-03-18-X; a left femur, DMR-KS-05-03-00-63; a left astragalus, DMR-KS-05-03-00-67.

Material description.

Upper dentition: a relatively worn M1 (DMR-KS-05-03-18-X) is nearly square in outline and displays a flattened ectoloph and a well developed crochet, medifossette, and posterior fossette (Fig. 12A) (for measurements, see Tab. 9).

Mandible and lower dentition: a hemi-mandible (DMR-KS-05-03-17-13) is strongly compressed laterally and preserves a partial mandibular ramus and body with worn cheek teeth, except for the m3 which is unbroken (Fig. 12 C–E) (for measurements, see Appendix 2). The lingual portion along the mandible is entirely broken. The mandibular depth below the m3 is higher than that of Rhinoceros sondaicus . An isolated p2 is relatively worn and broken at its posterior part (Fig. 12B). At the lingual side of the p2, the anterior valley is slightly developed, whereas the posterior valley is prominent.

Postcranial remains: an isolated femur (Fig. 12F, G) and astragalus are comparable in size to Rhinoceros unicornis , but are larger than Rhinoceros sondaicus ( Guérin 1980) (for measurements, see Appendix 1).

Taxonomic remarks and comparisons.

We assign the M1 (DMR-KS-05-03-18-X) to Rhinoceros unicornis according to the presence of the flattened ectoloph and enclosed medifossette (on a worn specimen), as well as its larger size than that of Rhinoceros sondaicus . These upper molar features are characteristic of Rhinoceros unicornis ( Colbert 1942). For the lower dentition, the size of the isolated p2 (DMR-KS-05-03-19-4) and the molar row length of the mandible DMR-KS-05-03-17-13 (Tab. 9) are comparable to those of recent Rhinoceros unicornis (31-32 mm and 147.5-161 mm, respectively) ( Guérin 1980: table. 6). Therefore, another species of rhinoceroses, Rhinoceros unicornis , is identified at Khok Sung.