幾何学的形態測定を用いたニホンザル（Macaca fuscata）の歯種同定の試み

Abstract

A lot of Japanese macaque (Macaca fuscata) fossil specimens have been discovered from the middle Pleistocene through Holocene deposits in Japan. Although some specimens are isolated molars, previous studies have not used them for statistic analyses, because it was difficult to identify their specific tooth class due to morphological similarities among teeth. In this study, we have applied a geometric morphometric method to explore the morphological differences among three classes of upper molars (M1-M3) in extant Japanese macaques, and assessed the reliability of the application of this method for fossil specimens. Canonical variate analysis revealed that there is a tendency for morphological differences among three classes of upper molars, as follows. M1 is characterized by the concavity of the external outline of the crown in the mesio-lingual region and its expansion on the buccal side of the mesial region and on the distal side of the buccal region, and lingual displacement of the protocone and hypocone. M2 tends to show the expansion of the external outline in the disto-lingual region and its slight concavity on the mesial side with mesial displacement of the metacone and hypocone. M3 is characterized by the expansion of the external outline in the mesio-lingual region and its concavity on the buccal side of the mesial region and on the distal side of the buccal region, and buccal displacement of the protocone and hypocone. All fossil molar specimens could be identified to their proper classes. Although improvement of this method is needed, it is now possible to identify the class of molars, even in isolated fossil specimens, and this may contribute to a better understanding of the evolutionary history of Japanese macaques.