The Dinosaur Heresies

The Dinosaur Heresies: New Theories Unlocking the Mystery of the Dinosaurs and Their Extinction is a 1986 book written by Robert T. Bakker.[1][2]

The Dinosaur Heresies
Paperback edition front cover,
Illustration by John Gurche (1985)
AuthorRobert T. Bakker
CountryUnited States
PublisherCitadel Press (current edition)
Publication date
Media typePrint/Hardcover
Pages481 pp.

The book sums up the extant evidence that indicates that dinosaurs, rather than being cold-blooded and wholly lizard-like, were warm-blooded, agile creatures more similar to modern birds than to lizards or other reptiles. Although controversial on publication in 1986,[3] much of The Dinosaur Heresies now represents the prevalent view in paleontological circles (although other parts have been outdated by more current research).[citation needed]

The main arguments used to show that dinosaurs were warm-blooded are:

  • Almost all animals that walk upright today are warm-blooded, and dinosaurs walked upright.
  • The hearts of warm-blooded animals can pump much more effectively than the hearts of cold-blooded animals. Therefore, the giant sauropod dinosaur Brachiosaurus must have had the type of heart associated with warm-blooded animals in order to pump blood all the way up to its head.
  • Dinosaurs such as Deinonychus led a very active life, which is much more compatible with a warm-blooded animal.
  • Some dinosaurs lived in northern latitudes, where it would have been impossible for cold-blooded animals to keep warm.
  • The rapid rate of speciation and evolution found in dinosaurs is typical of warm-blooded animals and atypical of cold-blooded animals.
  • The predator/prey ratio of predatory dinosaurs to their prey is a signature trait of warm-blooded predators rather than cold-blooded ones.
  • Birds are warm-blooded. Birds evolved from dinosaurs, therefore a change to a warm-blooded metabolism must have taken place at some point; there is far more change between dinosaurs and their ancestors, the archosaurs, than between dinosaurs and birds.
  • Warm-blooded metabolisms are evolutionary advantages for top predators and large herbivores; if the dinosaurs had not been warm-blooded, there should be fossil evidence showing mammals evolving to fill these ecological niches. No such evidence exists; in fact, mammals by the end of the Cretaceous had become smaller and smaller from their synapsid ancestors.
  • Dinosaurs grew rapidly, evidence for which can be found by observing cross-sections of their bones.


  1. ^ Kakutani, Michiko (1986-11-08). "BOOKS OF THE TIMES; Dinosaur Mysteries". The New York Times. Retrieved 2015-01-06.
  2. ^ "Review of The Dinosaur Heresies by Robert T. Bakker". Kirkus Reviews. 21 November 1986.
  3. ^ Horner, John R. (1988). "The Dinosaur Heresies. New Theories Unlocking the Mystery of the Dinosaurs and Their Extinction. Robert T. Bakker". The Quarterly Review of Biology. 63 (2): 210–211. doi:10.1086/415850. ISSN 0033-5770.