Re: [Re: [Re: Non-serpentine lacertids (was RE:WHAT'S GOING ON?)]]

["T. Mike Keesey" <tmk@dinosauricon.com>]

On Wed, 5 Jul 2000 ELurio@aol.com wrote:

> Calling birds reptiles is invalid for two reasons, reptiles in the tradtional 
> sense is a very different beast than a bird, i.e., reptiles are ectothermic 
> and birds are not, reptiles have three and a fraction chambered hearts, and 
> birds have four chambered hearts....we can go on and on.

One other comment -- many fossil taxa of traditional Reptilia likely did
have four-chambered hearts, since the crocodylian condition is supposed to
be derived from a four-chambered heart. This includes at least
part of non-crocodylian Pseudosuchia, all of non-avian Ornithosuchia
(including traditional Dinosauria) and possibly more basal
Archosauromorpha as well.

The recent _Thescelosaurus_ find may be direct evidence of this.

It is also arguable whether certain members of traditional Reptilia
(Therapsida, Ornithodira) were ectothermic.

____________________________________________________________________________
T. Michael Keesey <tmk@dinosauricon.com> | AIM <Ric Blayze> | ICQ <77314901>
                 My Worlds <http://dinosauricon.com/keesey>
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