The origin of snakes (Serpentes) as seen through eye anatomy

Christopher L. Caprette*, Michael S. Y. Lee, Richard Shine, Allie Mokany, Jerry F. Downhower

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

56 Citations (Scopus)


Snakes evolved from lizards but have dramatically different eyes. These differences are cited widely as compelling evidence that snakes had fossorial and nocturnal ancestors. Their eyes, however, also exhibit similarities to those of aquatic vertebrates. We used a comparative analysis of ophthalmic data among vertebrate taxa to evaluate alternative hypotheses concerning the ecological origin of the distinctive features of the eyes of snakes. In parsimony and phenetic analyses, eye and orbital characters retrieved groupings more consistent with ecological adaptation rather than accepted phylogenetic relationships. Fossorial lizards and mammals cluster together, whereas snakes are widely separated from these taxa and instead cluster with primitively aquatic vertebrates. This indicates that the eyes of snakes most closely resemble those of aquatic vertebrates, and suggests that the early evolution of snakes occurred in aquatic environments.

Original languageEnglish
Pages (from-to)469-482
Number of pages14
JournalBiological Journal of the Linnean Society
Issue number4
Publication statusPublished - Apr 2004
Externally publishedYes


  • Adaptation
  • Alethinophidia
  • Ophthalmic morphology
  • Parsimony analysis
  • Scolecophidia
  • Vertebrate evolution


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