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Re: warm-bloodedness

Ken Kinman wrote:

    The crocs and turtles and rest of the "reptiles" didn't diversify
anywhere near the extent that birds and mammals did, so they have never
seen as candidates for elevation to class status.

This is surely a fallacious argument! We know of far more crocodylomorph taxa in the Mesozoic than we do birds. Am I correct in perceiving that your assessment of "diversity" is based on the _modern_ number of bird taxa? Also, what is the "magic number" at which diversity becomes sufficient to stand up and be recognized? Why not use morphological distinctiveness? For example, the modern _Sphenodon_ is very distinctive compared to other taxa -- does it get its own group for this reason? It's certainly not very diverse!

Jerry D. Harris

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