Postsacral vertebral morphology in relation to tail length among primates and other mammals

This study quantifies postsacral vertebral morphology among living primates and other mammals known to differ in relative tail length (RTL). Linear and angular measurements with known biomechanical significance were collected on the first, mid‐, and transition proximal postsacral vertebrae, and their relationship with RTL was assessed using phylogenetic generalized least‐squares regression methods. Compared to shorter‐tailed primates, longer‐tailed primates possess a greater number of postsacral vertebral features associated with increased proximal tail flexibility (e.g., craniocaudally longer vertebral bodies), increased intervertebral body joint range of motion (e.g., more circularly‐shaped cranial articular surfaces), and increased leverage of tail musculature (e.g., longer spinous processes). These observations are corroborated by the comparative mammalian sample, which shows that distantly‐related short‐ (e.g., Phascolarctos, Lynx) and long‐ (e.g., Dendrolagus, Acinonyx) tailed nonprimate mammals morphologically converge with short‐ (e.g., Macaca tonkeana) and long‐ (e.g., Macaca fascicularis) tailed primates, respectively. Multivariate models demonstrate that the variables examined account for 70% (all mammals) to 94% (only primates) of the variance in RTL. Results of this study may be used to infer the tail lengths of extinct primates and other mammals, thereby improving our understanding about the evolution of tail reduction/loss. Keywords: tail le...

Source: The Anatomical Record Part B: The New Anatomist - August 11, 2014 Category: Anatomy Authors: Gabrielle A. Russo Tags: Full Length Article Source Type: research