Postcranial adaptations for leaping in primates

Leaping primates are specialized for hindlimb-propelled locomotion within a rboreal habitats. As a group, they include members of Galagonidae, Lemurifo rmes and Tarsiidae. Postcranial characters analysed here include humeral an d femoral diaphyseal rigidity, articular surface areas and lengths. Data fo r leaper taxa are compared with corresponding data for less specialized sma ll primates. The more generalized comparative primates include both closely related prosimians and distantly related platyrrhines (New World monkeys). In addition, the leapers are subdivided for further analysis according to body size and taxonomic association. Questions addressed concern the identi fication of functionally and/or phylogenetically linked traits in leaper po stcrania. Results indicate that leapers as a group have relatively higher f emoral diaphyseal rigidity and longer femora than do more generalized prima tes. These traits are also present in Pithecia pithecia, a platyrrhine leap er included for comparison. These enhanced properties probably function in resisting large hindlimb forces incurred during leaping, and in producing l onger, more efficient leaps. Most of the large-bodied lemuriform leapers ar e further distinguished in having relatively bigger femoral heads and reduc ed humeral rigidity. The small-bodied leapers, galagonids and tarsiids, do not differ in either femoral head surface area or in any of the humeral pro perties from more generalized primates. Pithecia has a large femoral head l ike lemuriforms, but it is not reduced in humeral rigidity. Aspects of hip joint structure and mobility may be related to femoral head size in lemurif orms and Pithecia. Explanations regarding reduced lemuriform humeral rigidi ty are also explored. Differences between lemuriform primates are also pres ent, most notably in aspects of the distal humerus. Indrids are characteriz ed by relatively reduced trochleae, while many lemurids have relatively sma ll capitula. These features are interpreted with regard to frequencies of s uspensory behaviour and quadrupedalism.