Regulation of Body Temperature by Some Mesozoic Marine Reptiles
Warm-Blooded Reptiles?
Existing reptiles are not thought to be endothermic, but what about extinct species? Three large extinct swimming reptiles, the ichthyosaurs, plesiosaurs, and mosasaurs, were active predators in the Mesozoic oceans. Bernard et al. (p. 1379; see the Perspective by Motani) investigated their metabolism by analyzing the oxygen isotopes in their teeth, compared with fish in deposits from a variety of ocean environments. The data imply that the ichthyosaurs and plesiosaurs, which were both pursuit predators, probably controlled their own temperature. The data for the mosasaurs, which are thought to have hunted by ambush, are more equivocal.
Abstract
What the body temperature and thermoregulation processes of extinct vertebrates were are central questions for understanding their ecology and evolution. The thermophysiologic status of the great marine reptiles is still unknown, even though some studies have suggested that thermoregulation may have contributed to their exceptional evolutionary success as apex predators of Mesozoic aquatic ecosystems. We tested the thermal status of ichthyosaurs, plesiosaurs, and mosasaurs by comparing the oxygen isotope compositions of their tooth phosphate to those of coexisting fish. Data distribution reveals that these large marine reptiles were able to maintain a constant and high body temperature in oceanic environments ranging from tropical to cold temperate. Their estimated body temperatures, in the range from 35° ± 2°C to 39° ± 2°C, suggest high metabolic rates required for predation and fast swimming over large distances offshore.
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Published In
Science
Volume 328 | Issue 5984
11 June 2010
11 June 2010
Copyright
Copyright © 2010, American Association for the Advancement of Science.
Submission history
Received: 25 January 2010
Accepted: 28 April 2010
Published in print: 11 June 2010
Acknowledgments
The authors thank M. Sander, B. McNab, and R. Seymour for preliminary discussions of these data during the workshop dedicated to “Sauropod gigantism” that was held in Bonn, Germany, in November 2008. We are also grateful to D. Brinkman and J. Gardner (Royal Tyrrell Museum), S. Etches and J. Clarke, G. Suan, J. Lindgren (Lund University), B. Kear (La Trobe University), and A. Schulp (Maastricht University) for providing samples. L. Simon and G. Escarguel helped us in the statistical treatment of data. This study was funded by both CNRS and the Institut Universitaire de France.
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