THE DIGITIGRADE HAND AND TERRESTRIAL ADAPTATION IN JAPANESE MACAQUES

Hand positions of Japanese macaques were observed during stable ground standing. It was revealed that Japanese macaques preferentially utili ze the digitigrade hand position. This agrees with previous claims tha t terrestrial primates tend to be digitigrade (e.g., Napier and Napier , 1967). In the digitigrade hand position, the second to fifth metacar pophalangeal joints are hyperextended with the metacarpi kept vertical . The proximal articular surface of the basal phalange is excavated pr oximodorsally in Japanese macaques to allow the hyperextension of the metacarpophalangeal joint. This skeletal specialization was observed i n the digitigrade baboon and the palmigrade colobus monkey also. Howev er, it was not seen in New World monkeys, apes and human. This skeleta l feature may suggest a retention of the semi-terrestrial origin of ce rcopithecids.