Fricke and Rogers (2000) applied a unique approach to the question of theropod metabolism. Their premise was that latitudinal effects on the oxygen isotope composition of meteoric water should be reflected more directly in endothermic homeotherms, because they maintain constant body temperature, than in ectothermic heterotherms, because they will be colder at higher latitudes. The isotope slope of theropods appears steeper than that of crocodiles, and it is possible and perhaps probable that the interpretation of theropod endothermy is correct. However, we believe the authors were premature in dismissing environmental factors and sample bias as explanations for their data. We...

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