Re: CROCODYLOMORPH ENDOTHERMY

[Dinogeorge@aol.com]

In a message dated 96-01-25 20:08:54 EST, pharrinj@PLU.edu (Nicholas J.
Pharris) writes:

>I'm also not convinced that ectotherms would need or could use "long, 
>erect limbs and tall bodies," hence my suspicion that these features 
>evolved in endothermic crocodilian predecessors (and that all other 
>animals which show these features--other thecodontians, all dinosaurs, 
>and all therapsids, including mammals--were/are also endothermic to one 
>degree or another).

Umm--they could and did use their long, erect limbs, etc. With the increased
blood aeration provided by the four-chambered heart (no possibility of mixing
of aerated with stale blood), the early thecodontians were much more active
animals than their proto-lepidosaur diapsid relatives. By the way, the
four-chambered heart also made the smaller thecodontians more efficient
climbers.

Four-chambered heart first, endothermy later. (Note that no extant endotherms
have three-chambered hearts, but one group of extant ectotherms--crocs--has
four-chambered hearts.)