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Re: Endothermic Crocs in Nature



On 15/4/05 4:08 pm, "MariusRomanus@aol.com" <MariusRomanus@aol.com> wrote:

The article also 
> goes on 
> to say that mitochondrial DNA from Jurassic crocs shows a high rate of
> evolution.... roughly equivalent to that seen in the mitochondrial DNA in
> modern 
> endotherms. All of this points to ancestral crocs with elevated metabolic
> rates 
> above that possessed by crocs today.
> 

Aaaargh! That Nature could have let such a poorly-structured, misleading
sentence go by... It really does say "The mitochondrial DNA from the
Jurassic crocodilians shows a high rate of evolution ? roughly equivalent to
that of mitochondrial DNA from modern endotherms".
    We hqve no mitochondrial DNA from Jurassic crocodilians. I doubt we have
any authentic DNA of any form for anything that old at all - DNA just isn't
anywhere near stable enough (a few thousand years is generally the limit).
Looking up the reference the Nature article gives for this sentence, I find
the title "The complete mitochondrial genome of Alligator mississippiensis
and the separation between recent archosauria (birds and crocodiles)".
    So I think 'Jurassic crocodilians' refers here to the age of the modern
crocodilian clade, while 'modern endotherms' means 'vertebrates which are
endotherms at the present time'. Altogether, very poor phrasing indeed.

    Cheers,

        Christopher Taylor