The Digitigrade Hand and Terrestrial Adaptation in Japanese Macaques

Abstract

Hand positions of Japanese macaques were observed during stable ground standing. It was revealed that Japanese macaques preferentially utilize the digitigrade hand position. This agrees with previous claims that terrestrial primates tend to be digitigrade (e.g., Napier and Napier, 1967). In the digitigrade hand position, the second to fifth metacarpophalangeal joints are hyperextended with the metacarpi kept vertical. The proximal articular surface of the basal phalange is excavated proximodorsally in Japanese macaques to allow the hyperextension of the metacarpophalangeal joint. This skeletal specialization was observed in the digitigrade baboon and the palmigrade colobus monkey also. However, it was not seen in New World monkeys, apes and human. This skeletal feature may suggest a retention of the semi-terrestrial origin of cercopithecids. © 1994, The Anthropological Society of Nippon. All rights reserved.