Nocturnality in Dinosaurs Inferred from Scleral Ring and Orbit Morphology

14 Apr 2011
Vol 332, Issue 6030
pp. 705-708


Variation in daily activity patterns facilitates temporal partitioning of habitat and resources among species. Knowledge of temporal niche partitioning in paleobiological systems has been limited by the difficulty of obtaining reliable information about activity patterns from fossils. On the basis of an analysis of scleral ring and orbit morphology in 33 archosaurs, including dinosaurs and pterosaurs, we show that the eyes of Mesozoic archosaurs were adapted to all major types of diel activity (that is, nocturnal, diurnal, and cathemeral) and provide concrete evidence of temporal niche partitioning in the Mesozoic. Similar to extant amniotes, flyers were predominantly diurnal; terrestrial predators, at least partially, nocturnal; and large herbivores, cathemeral. These similarities suggest that ecology drives the evolution of diel activity patterns.

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Published In

Volume 332 | Issue 6030
6 May 2011

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Submission history

Received: 5 November 2010
Accepted: 16 February 2011
Published in print: 6 May 2011


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Acknowledgments: We thank D. Brinkmann, S. Carlson, I. Schwab, G. Vermeij, and P. Wainwright for comments. C. Cicero, A. Engilis, I. Engilis, D. Evans, M. Flannery, P. Holroyd, M. Koelbl-Ebert, J. McGuire, C. Mehling, M. Norell, R. Papendieck, O. Rauhut, M. Sander, K. Seymour, B. Shaffer, D. Unwin, X. Xu, and Z. Zhou granted specimen access. The project was supported by NSF grant EAR 0551024 to R.M. and Durrell Funds of the Department of Geology, University of California Davis, an M. A. Fritz Award of Royal Ontario Museum, a doctoral stipend of German Academic Exchange Service, and a postdoctoral fellowship of German Research Foundation to L.S.



Lars Schmitz* [email protected]
Department of Evolution and Ecology, University of California, Davis, CA 95616, USA.
Department of Geology, University of California, Davis, CA 95616, USA.
Ryosuke Motani
Department of Geology, University of California, Davis, CA 95616, USA.


To whom correspondence should be addressed. E-mail: [email protected]

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