Tactile tips, toes & tails

The prehensile tail, capable of suspending the entire body weight of an animal, is thought to have evolved twice (in parallel) in New World monkeys (Platyrrhini): once in the monophyletic Atelinae ( Alouatta, Ateles, Brachyteles, Lagothrix ), and once in Cebus . This line of reasoning derives primarily from osteologic evidence suggesting similar mechanical structure of the prehensile tail in these two groups – both atelines and Cebus have caudal vertebrae capable of withstanding significantly higher bending stresses than nonprehensile‐tailed platyrrhine caudal vertebrae. This study focuses on the soft‐tissue similarities between atelines and Cebus , when compared against nonprehensile‐tailed platyrrhine taxa. Specifically, atelines and Cebus share similar pinnation angles, fiber lengths, and physiologic cross‐sectional areas of the prime lateral flexors of the tail (mm. intertransversarii caudae). The similarities in structure of these muscles indicate that the mm. intertransversarii caudae of atelines and Cebus are capable of producing higher contractile forces than those of nonprehensile‐tailed platyrrhines without any trade‐off in contraction velocity. These parallels are remarkable given that the skin of the tail is thought to differ dramatically between atelines and Cebus vis‐à‐vis Meissner's corpuscle density – anatomy associated with high tactile precision and prehension. Supported by NSF BCS‐0550676.