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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
> endotherms. All of this points to ancestral crocs with elevated metabolic
> 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.