ABSTRACT
This chapter provides a preliminary account of a natural locomotor group among the primates. The animals concerned are arboreal, have a vertical clinging posture at rest and are well adapted to a leaping mode of progression during which the hindlimbs, used together, provide the propulsive force. The morphology of such forms as Propithecus and Tarsius is generally regarded as a specialisation derived from a primitive quadrupedal primate morphology. However, when the known postcranial material of early fossil Eocene prosimians is considered in the light of vertical clinging and leaping adaptations, a different picture of the locomotor adaptations of early primates emerges. By the middle of Eocene, a large number of primate forms had appeared for which the vertical clinging and leaping type of locomotion has been inferred on osteological grounds.
