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Fwd: re: pterosaurs and dinosaurs



David Peters sent me the below message. He clearly
favors a derivation of pterosaurs within the
prolacertiforms and even disputes the dinosauromorph
affinities of Scleromochlus. Most interestingly he
states that Coseosaurus has caudal hairs.

It would be great if Renesto Silvio could commnent on
these matters 

--- David Peters <davidrpeters@earthlink.net> wrote:
> Date: Wed, 02 Oct 2002 07:26:02 -0500
> From: David Peters <davidrpeters@earthlink.net>
> To: a_ekaterina@yahoo.com
> Subject: re: pterosaurs and dinosaurs
> 
> Dear Katerina,
> 
> The Ornithodira (dinos, pteros and Scleromochlus) is
> a chimaera made up
> of dissimilar clades showing convergent characters
> based on bipedalism.
> 
> Scleromochlus is a basal crocodylomorph. Like them
> it has a short neck
> of only six or seven vertebrae, a skull wider than
> tall, and a calcaneal
> heel, among other characters not shared by dinos.
> See my abstract in
> this year's SVP meeting agenda.
> 
> Pterosaurs are derived prolacertiforms, closest to
> Cosesaurus,
> Sharovipteryx and Longisquama, with whom they share
> an antorbital
> fenestra without a fossa. They retain an elongated
> manual digit IV > III
> > II > I and a reduced or absent manual digit V.
> Also note that the
> caudofemoral anchors are all greatly reduced
> producing an attenuated
> tail with implications for complete elimination of
> the retractor muscles
> of the femur and default replacement by the rotator
> muscles of the
> pelvis. You won't find that in dinos. And the key
> synapomorphy of the
> little prolacertiforms is that big pedal digit V,
> which is greatly
> reduced in the other "ornithodires".
> 
> So ptero-hair is not homologous with feathers if the
> above scenario is
> correct. The last common ancestor of pterosaurs and
> dinos would be
> Prolacerta. Ptero-hair of the type described by
> Czerkas is restricted to
> pterosaurs, as far as I know, but Cosesaurus and
> anurognathids had long
> caudal hairs, in the pattern of giraffe tails.
> 
> Hope this helps. Share with the group if you wish.
> 
> David Peters



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