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Re: my piece on clades



At 08:48 PM 12/1/97 +0000, wa105@mead.anglia.ac.uk 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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