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Re: New refs (long)




DinoBoyGraphics@aol.com wrote:

This is one of those false truisms that permeates dinosaur paleontology. It usually goes something like this: "Since dinosaurs displayed such a striking range of size, they probably displayed a similar range of metabolic adaptations." There is absolutely no support for this amongst extant animal groups.

Are you kidding???!!!

I'll list just a few "extant animal groups" that display a range of metabolisms:

Mammals: Monotremes have lower metabolic rates than other mammals, and in many ways appear closer to the ectothermic condition.

Sharks: Certain members of the lamniform branch (Lamnidae, which includes the Great White Shark and makos) show partial endothermy: they can raise the temperature of muscles and certain organs above that of the surrounding sea water.

Fishes: Members of the Scombridae (includes mackerel and tunas) also display regional endothermy. This is not typical for fishes.

Insects: Some insects show an impressive degree of temperature regulation, especially considering their small body size (e.g. sphinx moths). This is not typical for insects.


Placental mammals show a larger size range (from a few grams to 200 metric tonnes) without anywhere near the variation in metabolic rate that is being implied for dinosaurs.

Placental mammals represent a very limited (and very artificial) clade for comparison to dinosaurs. Would you say that _Coelophysis_ and _Brachiosaurus_ had the same metabolism as any modern bird? If you don't, then you're argument is already dead in the water. If you do, then you're on your own...


Supposing a larger range of metabolic rates directly contradicts the analysis by analogy method,

All your math pertains to placental mammals. You're assuming (very bravely) that Placentalia constitute a satisfactory analog for the Dinosauria. However, no extant land mammal has ever achieved the dimensions of the largest sauropods - or even the largest hadrosaurs. Your choice of the placental clade of mammals for comparison is a Strawman.


and so requires positive evidence from the fossil record (or other extant groups).

The fact that some dinosaurs were feathered and (as far we can tell) all dinosaurs were not is positive evidence for metabolic variation within the Dinosauria.





Tim

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