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Re: my piece on clades
At 08:48 PM 12/1/97 +0000, firstname.lastname@example.org wrote:
> "Dimetrodon is a mammal-like reptile. And one of the features of all
> reptiles is a scaly, dry skin. It didn't have hair or sweat glands"
>But with the benefit of the cladistic approach, I'd say:
> "Dimetrodon is a synapsid. Living synapsids (mammals) all have hairy,
> glandular skin. The closest outgroup we know enough about is the Diapsida,
> with scales (sometimes feathers too) and no glands. The next outgroups are
> amphibians and lungfish, both of which have glandular skin. Amphibians
> have no scales, I don't know about lungfish. So from what I know, it's
> most likely that secretory skin is the primitive condition, retained in
> Dimetrodon. There is no phylogenetic evidence either way on the hair."
And just to add to this, it's been mentioned on this List that skin
impressions have been found of a pelycosaur (perhaps _Dimetrodon_ itself)
suggesting glandular skin....
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