hess@convex.com (Mark Hess) (12/08/89)
I am in th middle of a debate here and would like pointers to references to
find current info on the following theories.
Dinosaurs were cold blooded.
Dinosaurs were warm blooded.
Dinosaurs were reptilian or at least most closely associated with reptiles.
Dinosaurs were not reptilian and in fact were closest to birds.
I would be thrilled to have people comment on the above theories, but please,
I need references for substantiation. The person with whom I am arguing
will not believe me unless I can point to these answers in published works.
I hope that this generates some healthy discussion.
markus
Mark Hess { uunet, uiucdcs, ut - sally, sun } !convex ! hess
Convex Computer Corporation hess @ convex.COM
UNIX System Administrationhaake@osprey.cvs.rochester.edu (Bill Haake) (12/12/89)
In article <3775@convex.UUCP> hess@convex.com (Mark Hess) writes: >I am in th middle of a debate here and would like pointers to references to >find current info on the following theories. > >Dinosaurs were cold blooded. >Dinosaurs were warm blooded. I don't have references handy, (they are at home) but I'll make a few comments. I took a class in herpetology (reptiles and amphibians) back in 1978. The professor, Harvey Pough, is an expert on energetics of modern day herps and so spent some time on the topic. He was a stickler on the correct usage of the jargon. In particular we learned that "warm blooded" and "cold blooded" are inaccurate terms. There are four other adjectives used to more precisely describe body temperature regulation, they are: endothermic - deriving energy from metabolic sources to control body temperature, usually at a level higher than the environment. Warm blooded is often used in situations where endothermic is the better adjective. Birds and mammals are the most often used examples of endotherms. There are also examples of fish and insects that I know of that use metabolic processes to raise their body temp. ectothermic - deriving energy from the environment to control body temperature, usually at a level higher than the environment. Cold blooded is often used to describe ectothermic organisms. It is very misleading because many animals, especially reptiles and amphibians can control their body temperatures by behavioral thermoregulation. They can maintain a remarkably constant, elevated body temperature simply by moving between sun and shade or by changing their orientation to the sun. homeothermic - maintaining a constant body temperature either by behavioral thermoregulation (ectothermic) or by metabolic means (endothermic). poikilothermic - having a varying body temperature. Thus most birds and mammals are homeothermic endotherms. They maintain a constant, elevated body temperature by burning lots of calories and producing heat internally. There are, however, exceptions. Some hummingbirds have such a large surface area/volume ratio that they cannot afford to maintain a high body temperature through times with no food intake i.e. at night. Consequently their body temperature drops during the night. Most herps are poikilothermic ectotherms, they regulate their body temperature using the sun as their primary energy source and consequently their temperature varies. Your question is about dinosaurs. Were they endotherms or ectotherms? Homeotherms or poikilotherms? I am pretty Bakker was the first to call the dinosaurs "warm blooded". At any rate he was an early, strong proponent for the idea. In 78, Pough thought Bakker was full of s**t. At that time Bakker was using three lines of evidence (unfortunately I can only remember two right now). One was the ratio of predatory dinosaurs to herbivorous dinosaurs in fossil sites. Endotherms burn lots of calories to maintain their high body temperatures, therefore they need lots of food. A population of prey animals will only support a certain number of predators. Because they would need so much more energy intake, the number of endothermic predators that a prey population can support is much smaller than if the predators were ectotherms. Bakker said that the ratio found in dinosaur communities was low enough to suggest that they were endothermic. Bakker also looked at the morphology of bone in dinosaurs. He found some strong similarities to the Haversian canal system found in mammals. He interpreted this to mean that the physiology was similar to mammalian bone physiology and that they maintained a high body temperature. Pough had objections to all of Bakker's lines of evidence. I can't remember for sure, but I think that Bakker had picked only sites that had the lowest ratio of predator/prey dinosaurs for the first argument. For the second line of evidence, Pough argued that because of their large size, dinosaurs would certainly have been homeotherms even if they were ectotherms. Heat is lost over the surface of an animal while it is stored as a function of the volume. It takes a long time for something as large as a dinosaur to cool down, expecially if it is trying not to cool down by using behavior to prevent heat loss. His point was that the bone stuff indicated a relatively high, constant body temperature (homeothermy) which is expected in any large animal, not endothermy which is what Bakker was suggesting. So dinosaurs were almost certainly homeotherms. The question is whether they were endothermic or ectothermic. You will probably get much better evidence both pro and con than I can remember from 1978. Be sure to look at from the point of view that dinosaurs did not *require* an internal heat source to maintain a high body temperature. I have some references at home on modern herp thermoregulation. Email me if you want them. I would like to see what the current lines of evidence are, so if no discussion starts here, please post a summary of your debate Mark! Bill Haake haake@cvs.rochester.edu (128.151.80.13) University of Rochester (716) 275-8680