Abstract
Abstract. The first fossil record of Duboisia (Boselaphini, Bovidae) from Thailand confirms that this genus is no longer endemic to Java, Indonesia. The new fossil material is a calvarium with horn cores (older than the Middle Pleistocene) collected from a sandpit at Tha Chang, Nakhon Ratchasima Province, north-eastern Thailand. The present specimen is provisionally allocated to a species of Duboisia aff. D. santeng, which has weaker precornual ridges and anterior keels on the horn cores than D. santeng from Early and Middle Pleistocene deposits of Java, but these species share basic characteristics of horn cores as follows: the lower half inclined backwards; the upper half curved upwards; cross section rounded triangular, antero-posteriorly compressed, and with medial and lateral keels. Morphological similarities between D. aff. santeng and D. santeng support a strong faunal interchange between continental South East Asia and Java before the Middle Pleistocene, and suggest that the genus Duboisia diverged from the other genera of Boselaphini in the “Siva-Malayan” region.
Highlights
South East Asia is geographically divided from the Indian subcontinent by the Himalayan–Tibetan Plateau, the IndoBurma Range, and the Ganges and Brahmaputra rivers
The Neogene fauna of continental South East Asia is similar to that of the Siwaliks, in the Indo-Pakistan area (e.g. Stamp, 1922; Colbert, 1938), but recent studies based on mammalian fossils from the Irrawaddy beds (Middle Miocene to Early Pleistocene) of Myanmar have demonstrated a faunal difference between the Siwaliks and Irrawaddy beds, which had increased since the Late Miocene or Early Pliocene due to forming zoogeographical barriers (Nishioka et al, 2015, 2018b; Takai et al, 2016)
What Duboisia species were distributed on the continental region of southern Asia has been discussed in previous studies (Hooijer, 1962; Moigne et al, 2016), but these fossil records based only on isolated teeth are still debatable in taxonomy because cranial morphology should be diagnostic of the genus Duboisia (Stremme, 1911; Hooijer, 1958)
Summary
South East Asia is geographically divided from the Indian subcontinent by the Himalayan–Tibetan Plateau, the IndoBurma Range, and the Ganges and Brahmaputra rivers. The latest Pliocene and Early Pleistocene Satir fauna from Java, Indonesia, is impoverished and unbalanced and includes mammals of “Siva-Malayan” origin, such as Hexaprotodon sivajavanicus (Hippopotamidae, Artiodactyla) and Sinomastodon bumiajuensis (Proboscidea) (Sondaar, 1984). These mammals have been traditionally believed as endemic species to Java (Van der Maarel, 1932; Hooijer, 1950), but to what degree island species differ from the original continental species from the Siwaliks and the Irrawaddy beds is insufficiently studied (Van der Geer et al, 2010).
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