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David Marjanovic 07 April 2002 wrote:
1) "Unnamed" is called "Amniotiformes" in
http://dinosauricon.com/taxa /tetrapoda.html.
If it is probable that diadectomorphs are amniote,
in my opinion, they should be placed within Amniota. "Amniotiformes" synonymous
of "Amniotomorpha" is already used in Dinosauricon cladogram to name the clade
that includes westlothiana. Why multiply names founded on soft
tissue?
2) Sure it can. Pisces has been
dismissed.
But not outside the door in the external world.
Since science needs to be divulged after all. The title of the beatiful book of
John A.Long is "The rise of fishes" not "The
rise of Craniates" as it would expected by orthodoxy for a book that start with
myxinidae.
Inside you can find cladograms mixed with popular
terms like: jawless fishes, ray finned fishes, etc.
T. Michael Keesey 08 April 2002 wrote:
1) This would suggest that epidermal scales are a
reptilian synapomorphy, and that the mammalian lineage (synapsida)
never had them. Either the ancestral amniote had
dermal scales, lost in both lineages, or it had smooth skin. The latter seems
more likely to me.
Also today there are synapsids with epidermal
scales, as has rat in the tail. The scales are the epidermal structure that is
present in all the actual amniote lineages, although rare in mammals. As far as
I know the alpha keratin (the only one in mammals) is also present
in reptilian scales covered by beta keratin that is an advanced character
of diapsids.
Ventral bony scales were found in pelycosaurs
(Romer, Laurin & Reisz in Treeof Life). The retaining of this ancestral
character demonstrates the need of belly protection in a sprawl pelycosaur. But
it is unlikely that the dermal scales were present all over the body, because
these heavy structures, in a terrestrial environmet, are destabilizing
and
penalizing of the speed (Frolich), it is more
probable, in my humble opinion, that the protection in the rest of the body of
the first amniotes was assured by light alpha keratin scales, on which base, the
diapsids joined the beta keratin.
It seems to me very improbable that, in a
competition with keratin-scaly sauropsids, the synapsids substitute the
dermal scales protection with a lissamphibian skin, considering also the fact
that their actual descendants testify the capability of the synapsid skin
to produce scales.
Actual lissamphibians evolved poison glands as an
antidote to the loss of bony protection, but this seems not happened in early
synapsids or, I think, we should see the survival of them in their descendants,
but mammals with poison glands in the skin are extremely rare. Moreover
lissamphibians being small, arboreal or fossorial, are more immune to
predation;
it seems to me not realistic to imagine
cotylorhyncus as a 350 Kgs. toad.
2) How can they diverge before sauropsids when they
are the sister group to_Sauropsida_ ? By definition, both diverged from each
other at the same time.
Perhaps is better, from my side, to say that
synapsids are the earliest monophiletic lineage that can be well demonstrated to
have diverged within amniota.
Alberto Arisi
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