Tail length estimation from sacrocaudal skeletal morphology in catarrhines

Abstract

Tail morphology in primates is important for interpreting functional adaptation and phylogeny. Tail length is probably the most remarkable trait. Establishing usable methods to predict the tail length of extinct primates is part of the basis for the reconstruction of primate evolution, particularly of hominoids. Previous studies revealed that sacral morphology often predicts tail length. However, most previous studies have only attempted this by using categories (short, long, etc.). A problem with those studies is that the range of short tail length is wide. Accordingly, this study aimed to quantitatively estimate tail length in catarrhines with intermediate tail lengths. Sacra and proximal caudal vertebrae (first to third) of 89 hybrid individuals between Japanese macaque (Macaca fuscata) and Formosan rock macaque (Macaca cyclopis) were measured. These hybrid macaques were phylogenetically controlled but varied greatly in their relative tail length (tail length/head and body length = 18.8-88.8%), and thus were an excellent sample to obtain general regression formulae to estimate catarrhine tail length. A total of 15 predicting models were devised and five formulae performed well. The utility of these formulae were confirmed by application to 15 species/subspecies of catarrhine taxa.

Functional and Systematic Implications of the Postcranial Anatomy of a Late Miocene Feline (Carnivora, Felidae) from Batallones-1 (Madrid, Spain)

“…Given this, the presence of well-developed mammillo-articular processes in extant species with long tails would suggest the inclusion of L. vallesiensis in this group. Russo and Shapiro (2011) on their study on primates, found that the development of the caudal transverse process of the sacrum separated "long" and "tailless" groups from the "short"/"very short" groups, although the study did not distinguish "short" and "very short" groups (Tojima 2013). In the case of our compared sample of felines, there is no clear relationship between the morphology of the caudal transverse process and the length of the tail, as for example Le.…”

A Tale of the Tail : A Comprehensive Understanding of the “Human Tail”

“…1 . The caudal vertebrae are part of the skeletal system that maintains the tail, which articulates posterior to the sacrum [ 28 ]. The morphology of the caudal vertebrae differs between the proximal and distal regions [ 2 , 3 , 13 , 22 , 29 ].…”

Relationship between sacral shape variation and phylogeny in Old World monkeys

“…Other studies have addressed the relationship between sacral morphological variation and tail length variation or body size. The caudal part of the sacrum (especially the final sacral vertebrae) tends to show morphological variations that reflect the number of caudal vertebrae articulating posteriorly and/or caudal musculature attaching to the sacrum (Ankel, 1965, 1972; Russo & Shapiro, 2011; Tojima, 2013, 2014, 2015; Ward et al, 1991). Most of these studies were aimed at fossilized samples to reconstruct the tail length of extinct species categorically or quantitatively.…”