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Dinosaur Physiology: Were Dinosaurs Warm-Blooded?

  1. Devon E Quick1,
  2. Willem J Hillenius2

Published Online: 19 SEP 2013

DOI: 10.1002/9780470015902.a0003323.pub2

eLS

eLS

How to Cite

Quick, D. E. and Hillenius, W. J. 2013. Dinosaur Physiology: Were Dinosaurs Warm-Blooded?. eLS. .

Author Information

  1. 1

    Oregon State University, Corvallis, Oregon, USA

  2. 2

    College of Charleston, Charleston, South Carolina, USA

Publication History

  1. Published Online: 19 SEP 2013

Abstract

To evaluate the possible physiology of dinosaurs, comparisons must be made with their closest living relatives: birds and crocodilians. Although crocodilians maintain ectothermic metabolic rates and have anatomy reflective of this, modern birds achieve high, endothermic metabolic rates through specialised soft tissues supported by unique skeletal attributes. Finding similar shared characters in dinosaurs that are functionally linked to metabolic rates in birds or crocodilians allows plausible reconstruction of dinosaur physiology. Examinations of dinosaur remains reveal no structures with clear functional association with bird-like respiratory or metabolic physiology, and in some cases indicate crocodilian-like anatomy. Consequently, dinosaurs were most likely ectothermic, with resting and maximal metabolic rates that were lower than those of modern mammals or birds. However, given the favourable Mesozoic climatic conditions, most dinosaurs were probably able to maintain high, constant body temperatures through behavioural or inertial thermoregulation.

Key Concepts:

  • Reconstructing the biology of extinct forms relies on comparison with living taxa that share the same specialised features linked to specific function.

  • Stable body temperature can be achieved through behavioural mechanisms or through virtue of large mass, and need not rely on a particular metabolic strategy.

  • The closest living relatives of dinosaurs are birds and crocodilians, which have widely different metabolic rates supported by different respiratory and skeletal anatomy.

  • Some dinosaur remains preserve evidence, such as postcranial pneumaticity, that may be superficially suggestive of modern bird-like respiratory anatomy, but they lack other features critical for the ability to ventilate bird-like lungs or achieve bird-like aerobic capacity.

  • No dinosaur remains show evidence of respiratory turbinates, a skeletal character functionally associated with modern endothermy.

  • Endothermy was not likely achieved in dinosaurs, but was first present in mid-Cretaceous birds.

  • Some dinosaurs may have increased aerobic capacity using a crocodilian-like ventilatory mechanism.

Keywords:

  • archosaur;
  • aerobic capacity;
  • birds;
  • dinosaurs;
  • endothermy;
  • ectothermy;
  • respiratory system evolution;
  • Mesozoic;
  • thermoregulation