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Re: [Re: Reptilia]



owner-dinosaur@usc.edu wrote:
> On Sun, 6 Dec 1998 Philidor11@aol.com wrote:

> 

> > So, definitions of reptilia are based on:

> > 1. 4 limbs/scales/not lactating

> So snakes aren't reptiles? 

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I believe he meant, descended from a tetrapod ancestor.

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The other two characters do not fossilize

> (well, scales do, but pretty rarely), so they don't make for a very good

> diagnostic characters. Is _Cynognathus_ a reptile? Is _Seymouria_? Is

> _Dimetrodon_?

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Ahh, that's where the following set comes in.

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> 

> > 2. the windows (fenestra) system I was quoting from Fastovsky & Weishampel

> > 1996

> > 

> > I'd appreciate it if anyone with a different definition could add it.  The

> > mutability in this field is very interesting to me.

> 

> The cladistic definition was mentioned before, but I'll mention it again:

> the most recent common ancestor of chelonians (turtles), _Sphenodon_

> (tuatara), squamates (lizards and snakes), and crocodylians, plus all of

> its descendants.

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The only problem I have with the cladistic definition is that it does not tell
one what the diagnostic features are. All it says is the most recent common
ancestor.

So what constitutes being the common ancestor?

Archosaur J

Jurassosaurus's Reptipage: A page devoted to the study of the reptilia

http://members.tripod.com/~jurassosauridae/index.html

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