Dinosaurs – Warm or Cold Blooded? (S/F)

A subject Jurassic Park explores significantly is whether or not dinosaurs were cold-blooded, warm-blooded, or something in between. Dr. Alan Grant remarks how for certain the dinosaurs are warm-blooded, especially the Brachiosaurus. The debate was started back in 1968 by Robert T. Bakker, a paleontologist studying under Dr. John Ostrom at the time. Ostrom was responsible for discovering Deinonychus, a theropod dinosaur from the Early Cretaceous. Bakker, Ostrom, and Gregory Paul are responsible for the “Dinosaur Renaissance” and are credited for depicting dinosaurs as hot-blooded and active creatures. Vertebrate paleontology has debated the subject extensively and dinosaurs have been found to showcase both cold and warm blooded traits.

What are the conditions for something to endothermic (Hot blooded) and ectothermic (cold-blooded)? Endothermy is found in mammals and birds, dinosaur descendants, and it means the animal generates internal heat to moderate body temperature. Ecothermy means that the animal relies on the environment to regulate body temperature. There’s evidence to support that dinosaurs were heterothermic, both traits of hot and cold blooded life styles can be found in dinosaurs with variance in daily, seasonally, or throughout their life cycles. As dinosaurs grew larger they had traits of cold blooded animals. Dinosaurs would also rely on their size to maintain their body temperature, this is known as gigantothermy.

Lines of evidence to support multiple metabolisms in dinosaurs ranging from heterotherms to gigantotherms in addition to endothermic and ectothermic traits. These include the origins of birds, bone microstructure, blood pressure, posture/gait, trackways, and metabolism (how long it takes for dinosaurs to reach adulthood), as well as geographic distribution. Other lines of evidence can be used to identify is predator prey ratios, but there is a problem as the fossil record is not entirely complete.