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Keywords:

  • Prosimians;
  • Foot anatomy;
  • Osteology;
  • Myology;
  • I-II Grasp;
  • Adapidae

Abstract

The grasping primate foot is one of the hallmark adaptations for the order Primates. Prosimian muscle and joint analysis indicates that there are two distinct primate grasping feet. The I–V opposable grasp, in which the hallux opposes the other four digits around a support, is the primitive grasp type utilized by cheirogaleids, lorisides, Daubentonia, and tarsiids. Lemurids and indriids, on the other hand, have a derived I–II adductor grasp, where the grasping action of the hallux and the second digit have been enhanced. This grasp seems to be in response to increasing body size and the use of vertical supports. North American adapids, which were large and possessed the I–V opposable grasp, were probably not able to utilize vertical supports frequently. The recognition of this innovative adaptation, the I–II adductor grasp, which is unique to Madagascar, extends our appreciation of prosimian locomotor capabilities.