On the Fossil Teeth of Stegolophodon pseudolatidens(YABE) from the Miocene Bed of the Abukuma mountains

Abstract

Stegolophodon has a pecular position in the taxonomy as well as in the phylogeny of order Proboscidea. In this article, some fossil teeth of Stegolophodon pseudolatidens (YABE) hitherto considered to be the earliest form of Stegolophodon were examined. The materials, DP4 and M1, were obtained from the upper part of the Asakawa Formation (lower Middle Miocene) at Kitashioko, Omiya-machi, Naka-gun, Ibaraki Prefecture, North-east Japan. The DP4 is first known in this species. Compared with other specimens of Stegolophodon (pseudolatidens, tsudai and shinshuensis), the ridge formula for the species is proposed as follows: [Figure omitted] Paleohistology of the teeth was also carried out, and some characteristics were clarified. The enamel area is generally composed of prisms with cross section of keyhole shape. No typical ginkgoleaf shaped cross section is observed. It may represent a basic pattern of the enamel structure of Stegolophodon.