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Ectothermy and the Success of Dinosaurs

Michael J. Benton
Evolution
Vol. 33, No. 3 (Sep., 1979), pp. 983-997
DOI: 10.2307/2407661
Stable URL: http://www.jstor.org/stable/2407661
Page Count: 15
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Ectothermy and the Success of Dinosaurs
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Abstract

The evidence for dinosaur endothermy is partly inconclusive, partly spurious and, of course, its interpretation is totally speculative. Extrapolations from studies of thermoregulatory physiology of living reptiles suggest that ectothermic dinosaurs could have achieved homeothermy inertially simply by being large. Endothermy is a costly attribute and it is argued that it would have been distinctly disadvantageous, as well as unnecessary, in dinosaurs (with the possible exception of small theropods). Mesozoic climates were generally warmer than at present and largely arid during the Late Triassic. It is suggested that ectothermy could have proved advantageous to archosaurs in the Late Triassic and may have contributed to the success of their replacement of the possibly endothermic mammal-like reptiles. Constant body temperatures without the necessity of consuming large quantities of food as in endotherms may have assured the continued success and diversification of dinosaurs in the warm Jurassic and Cretaceous. A possible temperature drop towards the end of the Cretaceous, together with increasing seasonality of climates and the introduction of temperate floras, in conjunction with the large size, naked skin and inertial homeothermy of dinosaurs, may have contributed to their extinction.

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