Comparative Anatomy of Caudal Musculature Attachments in Catarrhines with Different Tail Length

Tail length in primates greatly varies and is considered an important feature for understanding primate adaptations and phylogeny. Especially in some catarrhines, tails have become extremely reduced. Previous studies suggested that some sacral morphology reflects tail length to reconstruct the process of tail reduction in catarrhines (Ankel, 1965, 1972; Ward et al., 1991; Russo & Shapiro, 2011; Tojima, 2013), but the reason why such morphology reflects tail length variation was not clarified. Generally, the muscles attached to bones must change together with the skeletal morphology. Thus, the musculoskeletal morphological variation in the sacro-caudal region must reflect differences of tail function, and it could be linked to the process of and the reason for tail reduction. In catarrhines, however, there have been few studies of caudal musculature (Howell & Straus, 1965; Swindler & Wood, 1982; Tojima, 2010) and the anatomical musculature data with different tail lengths are still incomplete. Therefore, this study aimed to provide an updated overview of caudal muscles in catarrhines and to clarify the relationships among caudal muscles, sacro-caudal skeletal morphology, and tail length variation. MATERIALS AND METHODS