Primary homologies of the circumorbital bones of snakes
Version of Record online: 30 APR 2013
Copyright © 2013 Wiley Periodicals, Inc.
Journal of Morphology
Volume 274, Issue 9, pages 973–986, September 2013
How to Cite
Palci, A. and Caldwell, M. W. (2013), Primary homologies of the circumorbital bones of snakes. J. Morphol., 274: 973–986. doi: 10.1002/jmor.20153
- Issue online: 19 AUG 2013
- Version of Record online: 30 APR 2013
- Manuscript Accepted: 2 MAR 2013
- Manuscript Revised: 31 JAN 2013
- Manuscript Received: 3 DEC 2012
- Alberta Innovates - Technology Futures (A.P.)
- NSERC Discovery Grant. Grant Number: #238458
- NSERC Accelerator Grant and Chair's Research Allowance
Some snakes have two circumorbital ossifications that in the current literature are usually referred to as the postorbital and supraorbital. We review the arguments that have been proposed to justify this interpretation and provide counter-arguments that reject those conjectures of primary homology based on the observation of 32 species of lizards and 81 species of snakes (both extant and fossil). We present similarity arguments, both topological and structural, for reinterpretation of the primary homologies of the dorsal and posterior orbital ossifications of snakes. Applying the test of similarity, we conclude that the posterior orbital ossification of snakes is topologically consistent as the homolog of the lacertilian jugal, and that the dorsal orbital ossification present in some snakes (e.g., pythons, Loxocemus, and Calabaria) is the homolog of the lacertilian postfrontal. We therefore propose that the terms postorbital and supraorbital should be abandoned as reference language for the circumorbital bones of snakes, and be replaced with the terms jugal and postfrontal, respectively. The primary homology claim for the snake “postorbital” fails the test of similarity, while the term “supraorbital” is an unnecessary and inaccurate application of the concept of a neomorphic ossification, for an element that passes the test of similarity as a postfrontal. This reinterpretation of the circumorbital bones of snakes is bound to have important repercussions for future phylogenetic analyses and consequently for our understanding of the origin and evolution of snakes. J. Morphol. 274:973–986, 2013. © 2013 Wiley Periodicals, Inc.