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Re: mesosaurs - what are they?



----- Original Message -----
From: "David Peters" <davidrpeters@earthlink.net>
Sent: Saturday, February 05, 2005 2:28 PM

My analysis places turtles outside of the diapsida, between
Procolophon and Anthodon. So now we're stuck with a potentially
problematic clade list.

I'll naïvely say that all you need now to arrive at published phylogenies are some anapsid synapomorphies. In Lee's analyses, at least, turtles do come out as


--+--*Procolophon*
 `--+--turtles
    `--+--*Anthodon*
       `--...

if you read this as

--+--Procolophonia
 `--+--turtles
    `--Pareiasauridae

.

If we allow that the ectopterygoid fused to the pterygoid in
turtles, as it appears, then this character is homologous and present
whether you call it a palatine fenestra or a suborbital fenestra. Either
way, present in basal sauropterygia and mesosaurs (the palate is on the
Internet, but I can send you the evidence).

Just so that I learn it -- does any of the skulls in fig. 1 of http://tolweb.org/accessory/Phylogeny_and_Classification_of_Amniotes?acc_id=462 have a suborbital fenestra?


As in Claudiosaurus, the last in the lineage to retain an
identifiable PP, so this character is present in Sauropterygia.

Except *C.* has stopped coming out as a sauropterygian. It's now close to but outside the crown group of Diapsida, for example in Müller's analysis.


And here is the fault with all prior cladistic analyses! All of
the above are obscure cranial characters.

Why "obscure"?

In my analysis, Mesosaurs share with either Pachypleurosaurus or
Lariosaurus  or both, 128 out of 139 characters

And all of those are the derived states???