The Middle Pleistocene vertebrate fauna from Khok Sung (Nakhon Ratchasima, Thailand): biochronological and paleobiogeographical implications Author Suraprasit, Kantapon Author Jaeger, Jean-Jacques Author Chaimanee, Yaowalak Author Chavasseau, Olivier Author Yamee, Chotima Author Tian, Pannipa Author Panha, Somsak text ZooKeys 2016 613 1 157 http://dx.doi.org/10.3897/zookeys.613.8309 journal article http://dx.doi.org/10.3897/zookeys.613.8309 1313-2970-613-1 0FDE9BAB3DD4402DB6E1177639C32D43 Taxon classification Animalia Artiodactyla Bovidae Capricornis sumatraensis (Bechstein, 1799) Referred material. A left M2, DMR-KS-05-03-18-16; three m3-DMR-KS-05-04-05-4 (right), DMR-KS-05-03-27-5 (left), and DMR-KS-05-03-28-10 (left posterior fragment). Material description. Isolated teeth are almost complete (for measurements, see Tab. 16), with the exception of the specimen DMR-KS-05-03-28-10 that preserves only a posterior lobe (Fig. 33G). Molars show typical features of Capricornis characterized by hyposodont crowns, smooth enamel, and distinct styles and stylids, and an absence of the ectostylids (Fig. 33). The parastyle, mesostyle, and metastyle on the M2 are perpendicular to the buccal wall (Fig. 33A). On the m3, the mesostylid is more developed than the other stylids and the posthypoconulidcristid protrudes posteriorly (Fig. 33C, E). Figure 33. Dental remains of Capricornis sumatraensis from Khok Sung: A-B DMR-KS-05-03-18-16, a left M2 in occlusal (A) and lingual (B) views C-D DMR-KS-05-04-05-4, a right m3 in occlusal (C) and buccal (D) views E-F DMR-KS-05-03-27-5, a left m3 in occlusal (E) and buccal (F) views G-H DMR-KS-05-03-28-10 in occlusal (G) and buccal (H) views. Table 16. Measurements (lengths and widths in millimeters) of molars of Khok Sung Capricornis sumatraensis .

Specimen

Length

Width

Taxonomic remarks and comparisons. We assign these isolated teeth from Khok Sung to Capricornis sumatraensis (Sumatran serow) because they are comparable in size and morphology to the extant specimens (Fig. 34). Among congeneric species, Capricornis sumatraensis is larger than Capricornis crispus as well as two goral species ( Naemorhedus goral and Naemorhedus caudatus ), but is smaller than Capricornis milneedwardsi . In addition, it differs from Capricornis crispus in having more developed metastylid and entostylid and a presence of back fossettes on the slightly worn m3 and from Capricornis milneedwardsi in having less developed metastylid and posthypoconulidcristid on the m3. Figure 34. Scatter diagrams of M2 and m3 lengths and widths of recent and fossil serows and gorals. The measurements of fossil specimens from Lang Trang, Thum Wiman Nakin, Thum Prakai Phet, and Tam Hang South are from de Vos and Long (1993) , Tougard (1998) , Filoux et al. (2015) , and Bacon et al. (2011) , respectively. Compared to other fossil records, Capricornis sumatraensis from Khok Sung is smaller than that from the Late Pleistocene of Lang Trang in Vietnam ( de Vos and Long 1993 ), Tam Hang South in Laos ( Bacon et al. 2011 ), Padang Cave in Sumatra ( Hooijer 1958 ), and Xianrendong in China ( Chen and Qi 1978 , Chen and Li 1994 ) (Fig. 34) and from the late Middle Pleistocene of Guanyindong ( Li and Wen 1986 ) in China. The Khok Sung material also matches morphologically that of the subspecies Capricornis sumatraensis kanjereus from the Middle Pleistocene of Yenchingkuo in China ( Colbert and Hooijer 1953 ) and from the late Middle Pleistocene of Thum Wiman Nakin in Thailand ( Tougard 1998 ). However, Capricornis sumatraensis from Khok Sung is larger than that from Thum Wiman Nakin and Naemorhedus from Thum Prakai Phet. It differs from Capricornis sumatraensis qinlingensis described from the middle Early Pleistocene of Gongwangling in northern China ( Hu and Qi 1978 , Zhu et al. 2015 ) in having its smaller size and less developed parastyle and metastyle on the M2. However, we do not assign the material to the subspecies level based on the few isolated teeth.