Fusion of sacrals and anatomy in Champsosaurus (Diapsida, Choristodera)

Author: Katsura, Yoshihiro

Source: Historical Biology: A Journal of Paleobiology, Volume 19, Number 3, September 2007 , pp. 263-271(9)

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Abstract:

Sacral centra are occasionally fused with or without severe deformation in Champsosaurus (Diapsida, Choristodera). The sympatrical occurrence of fusion and non-fusion of sacra in adults through their evolution questions that sacral fusion represents the final form of a simple ontogenetic change or specific variation. Females are proposed to possess more robust limb bones than males because they are considered to have been more terrestrial due to the nesting behaviour on land. The coincidental occurrence of fusion of sacral centra without severe deformation and more robust limb bones in same individuals suggests that sacral fusion is a phenomenon occurring in females as a result of terrestrial adaptation for reproductive activities. Sacral fusion associated with severe deformation is considered a pathological condition although its etiology and factors remain undefined.

Keywords: Sacral fusion; Champsosaurus; sexual dimorphism; ethology; Late Cretaceous-Early Eocene; North America

Document Type: Research article

DOI: http://dx.doi.org/10.1080/08912960701374659

Affiliations: 1: Gifu Prefectural Museum, Seki City, Gifu, Japan

Publication date: 2007-09-01

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