Feeling the Heat

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Science  06 Oct 2000:
Vol. 290, Issue 5489, pp. 15
DOI: 10.1126/science.290.5489.15c

Thermoregulation in large dinosaurs has been a preoccupation of palaeontologists for many years. Were they like modern reptiles (ectotherms), which rely on external sources of heat to maintain body temperature, or like mammals (endotherms), which maintain a relatively constant temperature via metabolic heat production? Evidence from fossil morphology has been inconclusive.

Fricke and Rogers take a new approach to this question, by measuring the oxygen isotope ratios found in tooth enamel of Cretaceous theropod dinosaurs and coexisting crocodilians across a range of latitudes. The isotope ratio is a signature of the temperature conditions under which bones and teeth originally were formed. The crocodilians showed a shallow spread of ratios consistent with ectothermy, while the dinosaurs showed a pattern similar to that of present-day endothermic mammals and birds. The door is now open to the investigation of the degree of thermal regulation across a wide range of fossil animals. — AMS

Geology28, 799 (2000).

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