Lower Miocene Cervoid Ruminants (Artiodactyla) from the Koura Formation, Matsue, Southwestern Japan

Dental fossils of an indeterminate small cervoid (Ruminantia, Artiodactyla, Mammalia) from the lower Miocene Koura Formation of southwestern Japan are described. The examined specimens of Cervoidea fam., gen. et sp. indet. consist of selenodont lower molars with plesiomorphic characteristics of early cervoids: a strong external postprotocristid (or Palaeomeryx-fold), a deep groove on the lingual wall of the internal postmetacristid, and opening posterior cristids between the postentocristid and the posthypocristid. The lower molars are similar in shape and size with those of Miocene Cervidae rather than Moschidae or Palaeomerycidae because the present specimens are comparable to those of Dicrocerus tokunagai, which is one of the lower/ middle Miocene cervids from northeastern Japan, and D. grangeri from the middle Miocene of China. The lower Miocene Nakamura Formation (ca. 19 Ma) of central Japan also yielded a small cervoid species sharing the lower molar characteristics with Cervoidea fam., gen. et sp. indet. from the Koura Formation, suggesting a faunal or biostratigraphical correlation between the two formations.