Osteological correlates and phylogenetic analysis of deep diving in living and extinct pinnipeds: What good are big eyes?
Article first published online: 21 MAR 2012
© 2012 by the Society for Marine Mammalogy
Marine Mammal Science
Volume 29, Issue 1, pages 48–83, January 2013
How to Cite
Debey, L. B. and Pyenson, N. D. (2013), Osteological correlates and phylogenetic analysis of deep diving in living and extinct pinnipeds: What good are big eyes?. Marine Mammal Science, 29: 48–83. doi: 10.1111/j.1748-7692.2011.00545.x
- Issue published online: 20 DEC 2012
- Article first published online: 21 MAR 2012
- Received: 31 August 2010 Accepted: 15 September 2011
- diving depth;
- phylogenetic independent contrasts;
Marine tetrapods have evolved different sensory solutions to meet the ecological challenges of foraging at depth. It has been proposed that pinipeds, like ichthyosaurs, evolved large eyeballs for such demands. Here, we test this hypothesis using morphological and diving data from a comprehensive data set (n= 54 species; 435 individual specimens), including living and extinct pinnipeds and other select carnivorans as outgroup taxa. We used bony orbit size as a proxy for eyeball size, and recorded associated skull measurements to control for relative changes in orbit size; for diving depth, we used the deepest dive depth reported in the literature. Our analyses included both standard regressions and those corrected for phylogeny (i.e., independent contrasts). Standard regression statistics showed orbit size was a significantly good predictor of diving depth for phocids and for pinnipeds overall, although there was no correlation for otariids. In contrast, independent contrasts showed little support for a relationship between orbit size and diving depth for any group broader than family level, although this approach did demonstrate deep diving has evolved multiple times in crown Pinnipedia. Lastly, using select fossil taxa, we highlight the need to test adaptive hypotheses using comparative data in an evolutionary context.