New species of Agriotherium (Mammalia, Carnivora) from the late Miocene to early Pliocene of central Myanmar

摘要

Here we describe a new species or giant short-raced fossil bears, Agnothenum myanmarensis sp. nov. (Ursidae, Carnivora), from the latest Miocene to early Pliocene Irrawaddy sediments in the Chaingzauk area, central Myanmar. A. myanmarensis has a short mandible and a deep premasseteric fossa, both of which are the typical feature of Agriotherium. There are two specimens discovered so far: in the type specimen the inferior border of the mandibular corpus is rectilinearly-shaped, the ml talonid is rather reduced, ml metaconid larger than the entoconid-entoconulid ridge, the diastema between canine and p4 is very short, and the postcanine teeth are so reduced that existing cheek teeth are very crowded. Agriotherium had been widely distributed from the late Miocene through Pleistocene in Europe, East Asia (China), North America, and South Africa, but no fossil record has been reported from Southeast Asia. Except its extreme short snout, A myanmarensis is most similar to that of the European form, Agriotherium insigne, rather than to the Asian species from Siwalik or China, such as Agriotherium palaeindicus, Agriotherium sivalensis, and Agriotherium inexpetans, suggesting the phylogenetic closeness to the European rather than to the South/East Asian forms.