Thermoregulation in Dinosaurs

Abstract

ANATOMICAL, physiological and ecological evidence has been assembled by Bakker¹ in an attempt to demonstrate that dinosaurs were endotherms. But critical parts of this evidence are less than convincing and may be interpreted differently. Bakker suggests that dinosaurs were built for sustained locomotion at moderate speeds and infers from this that dinosaur energy metabolism was endotherm-like. But I consider it likely that dinosaurs, like terrestrial mammals, generally moved at low speeds and only reached maximum speeds in short bursts. The cheetah (Acinonyx jubatus) can attain 97 km h⁻¹ over a distance of 370 m (ref. 2), but soon slows down if the prey is not caught inside this distance. Thus the cheetah's top speed is maintained for about 15 or 20 s. Lizards are capable of fast running in anaerobic bursts lasting 20 s or so¹ and a similar mechanism could have permitted sophisticated cheetah-like predation in communities of ectothermic dinosaurs.