Respiratory physiology of the dinosaurs

Summary Dinosaurs were among the most distinctive and successful of all land vertebrates. Attempts at reconstructing their biology have become commonplace. However, given the absence of closely comparable living models, deciphering their physiology necessarily remains speculative and determination of their metabolic status has been particularly problematical. Nevertheless, many paleontologists have advocated the notion that they were probably ‘‘warm-blooded’’ (endothermic), thus providing a model supposedly essential to the interpretation of these animals as having led particularly active, interesting lives. Those suppositions notwithstanding, the apparent absence of respiratory turbinates in dinosaurs, as well as likely ectothermic patterns of thermoregulation in very early birds, argues strongly that these animals were unlikely to have achieved the metabolic status of modern terrestrial endotherms. These data are not necessarily inconsistent with current models of active lifestyles of dinosaurs. BioEssays 20:852‐859, 1998. r 1998 John Wiley & Sons, Inc.