Functional morphology of mammalian sacra and caudal vertebrae : implications for tail loss and positional behaviors in extinct primates

Russo, Gabrielle Antoinette

Functional morphology of mammalian sacra and caudal vertebrae : implications for tail loss and positional behaviors in extinct primates

dc.contributor.advisor	Shapiro, Liza J.
dc.creator	Russo, Gabrielle Antoinette	en
dc.date.accessioned	2013-09-25T15:25:26Z	en
dc.date.issued	2013-08	en
dc.date.submitted	August 2013	en
dc.date.updated	2013-09-25T15:25:26Z	en
dc.description	text	en
dc.description.abstract	All living hominoids are characterized by taillessness and adaptations to orthograde (upright) trunk posture. Accordingly, these features have importance for our understanding of ape origins, evolutionary relationships and positional behaviors. Despite extensive study of the hominoid postcranial skeleton, researchers continue to face difficulty identifying taillessness and orthogrady from fossil material. In part, difficulties persist because although the Miocene fossil record indicates that the evolution of tail loss and orthogrady was decoupled, previous research has focused primarily on how the skeletal anatomy of extinct apes resembles that of living apes, in which these traits appear in conjunction. The remarkable diversity in tail lengths and positional behaviors exhibited by other mammals presents a valuable opportunity to employ the strength of the comparative method for testing functional hypotheses. The goal of this dissertation is to identify anatomical correlates of tail length and positional behaviors from sacral and caudal vertebral morphology among primates and other mammals in three studies. The first study examines the relationship between trabecular structure in the first sacral vertebra and positional behaviors (N= 78 primates). The second study quantifies aspects of internal (N=78 primates) and external (N= 472 mammals) sacral anatomy for correlates of relative tail length. The third study evaluates the functional morphology of caudal vertebrae among nonprehensile-tailed primates and other mammals that vary in relative tail length, offering additional insight into the anatomy associated with tail loss (N=333). The relationship between trabecular structure in the proximal sacrum and positional behaviors among living primates is somewhat unclear. Some trabecular parameters in the distal sacrum appear to have a relationship with tail length. Results support the functional links between previously and newly defined metrics from the external morphology of sacra and caudal vertebrae, and relative tail length, among primates and other mammals. Identified anatomical correlates from the extant primate sample are used to reconstruct the tail lengths of extinct primates. From the sacral data, Proconsul is reconstructed as tailless, Archaeolemur likely possessed a long tail, and Palaeopropithecus, Megaladapis and Epipliopithecus had short tails. From the caudal vertebrae data, Archaeolemur is reconstructed as possessing a long tail and Palaeopropithecus is reconstructed as having a short tail.	en
dc.description.department	Anthropology	en
dc.format.mimetype	application/pdf	en
dc.identifier.uri	http://hdl.handle.net/2152/21313	en
dc.language.iso	en_US	en
dc.subject	Functional morphology	en
dc.subject	Sacrum	en
dc.subject	Tails	en
dc.subject	Positional behaviors	en
dc.subject	Hominoid evolution	en
dc.subject	Subfossil lemurs	en
dc.title	Functional morphology of mammalian sacra and caudal vertebrae : implications for tail loss and positional behaviors in extinct primates	en
thesis.degree.department	Anthropology	en
thesis.degree.discipline	Anthropology	en
thesis.degree.grantor	The University of Texas at Austin	en
thesis.degree.level	Doctoral	en
thesis.degree.name	Doctor of Philosophy	en