Comment on the evolution of claw-like nails in callitrichids (marmosets/tamarins).

A recently proposed scenario for the evolution of a unified complex of exudativory, vertical clinging, and claw-like nails in callitrichids is examined. Consideration of behaviors and morphologies exhibited by Callimico goeldii leads to a decoupling of this "complex," with the early occurrence of claws and vertical clinging in the callitrichid lineage and only later, in some descendents, the development of exudativory and possible related behaviors.