1989 年 28 巻 2 号 p. 95-102
The fissure sediments at Site 5 of Yage Quarry are composed mainly of brown mud, and yield abundant mammalian remains. Bones of large mammals from the sediments are dated 18, 040±990y. B. P. by the 14C method. The assemblage comprises at least 15 taxa of mammals. Three of them (Anourosorex japonicus, Microtus cf. brandtioides, and Ursus cf. arctos) are not currently present in Honshu. However, the other taxa are referable to the elements of the lowlands and low mountains of the present Honshu. The geological age of the assemblage approximately corresponds to the coldest phase of the Würm glacial time. However, it lacks the elements of high mountains and colder areas which are found in the contemporary assemblages from F4 of Kumaishi-do Cave and Horizon N of Kannondo Cave Site. These facts seem to indicate that the climatic and vegetational conditions of those days were considerably different in Yage Quarry and the above two localities.
Taking the data for other fossil localities into consideration, it is inferred that the above-mentioned three taxa vanished from Honshu between 18, 000 and 14, 000y. B. P.