Implications for dinosaur ecology

Based upon our experimental results, we decided to analyze the implications of our findings to the question of thermal biology of very large reptiles. We focused our efforts on another large class of reptiles, the mammal-like reptiles that were prominent around the Permian-Triassic transition (Paleozoic to Mesozoic).

We focused our efforts on modeling heat exchange in two similarly-sized mammal-like reptiles. Dimetrodon sports a large sail on its back, with skin supported on the neurohypheses of the vertebrae. The sail has a rich blood supply, and Dimetrodon occurs over a large range of body sizes. We also modeled heat exchange in mammal-like reptiles without sails.

We found that the sail played a greater and greater role as a blood controlled heat exchanger at larger and larger body sizes. Thus, large reptiles, if they are to control heat exchange with blood circulation at all, must do so through the development of elaborate systems of ancillary heat exchange fins, like the Dimetrodon sail, or the crests of dinosaurs like Stegosaurus.

The benefits a large reptile would derive from having ancillary heat exchange fins would be an earlier start time in the day for foraging (less than an hour), and a longer time for foraging at the end of the day (also about an hour).

Further reading

Tracy, C. R., J. S. Turner, et al. (1986). A biophysical analysis of possible thermoregulatory adaptations in sailed pelycosaurs. The Ecology and Biology of Mammal-like Reptiles. N. Hotton III, P. D. MacLean, J. J. Roth and C. Roth: 195-206.

Turner, J. S. and C. R. Tracy (1980). Hemodynamics and heat exchange in reptiles with limbs. American Zoologist 20: 769.

Turner, J. S. and C. R. Tracy (1980). The interaction of morphology and physiology in energy exchange of reptiles. Bull Ecological Soc of America 61: 93.

Turner, J. S. and C. R. Tracy (1986). Body size, homeothermy and the control of heat exchange in mammal like reptiles. The Biology and Ecology of the Mammal-like Reptiles. N. Hotton III, P. D. MacLean, J. J. Roth and C. Roth. Washington, D C Smithsonian Institution Press: 185-194.

Blood flow pages

Heat exchange

Why alligators?

What we did

What we found