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Re: New refs (short)



Nick Pharris <npharris@umich.edu> wrote:

Crocs invaded (and still inhabit) a niche (aquatic ambush predation) in which, it has been argued, it is beneficial to be ectothermic.

You could be right. I don't know.

Placental mammals have occupied many of the same niches occupied by dinosaurs (large herbivore, small flyer), and yet none of these have become ectothermic.

Land mammals never got as large as the larger sauropods. I think that tells us something. And all "small flyers" in the Tetrapoda are endothermic (definite for bats and birds; probable for pterosaurs)


Thus, there is no reason to think that dinosaurs produced secondarily ectothermic forms.

I baulk at calling any dinosaur 'ectothermic'. As I said, modern reptiles and birds+mammals sit at opposite ends of a wide metabolic spectrum. It is likely that most non-avian dinosaurs sat somewhere in the middle. Endothermy is not cut from whole cloth, and there is no reason to believe that larger dinosaurs did not have intermediate metabolisms.




Tim

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