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Prolacertiforms are not lepidosauriforms (was RE: Pterosaurian Pedal Clinching (Batman! :) ))



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Jaime A. Headden
>
>   Given either of the two theories regarding pterosaur
> evolution, one being the archosaur derivative, and the
> other lepidosauriform derived, both have ancestors
> that could be and probably were, scansorial or
> arboreal.
>
>   2) Lepidosauriform (see work by Peters, both
> published and on-line), where the ancestor is
> lizardlike and steadily elongated the forelimbs rather
> than the hindlimbs, as in archosaurs, with the
> exception of some certain maniraptorans (i.e.,
> *Sinornithosaurus*).
>

A correction: Peters (at
http://home.stlnet.com/~azero/Pterosaur_Homepage.htm) considers pterosaurs
to be derived prolacertiforms.  Despite their name, prolacertiforms are NOT
particularly close to lepidosaurs, and a not even lepidosauromorphs.  They
are instead archosauromorphs.

So the two main hypotheses of pterosaur origins still agree on them being
archosauromorphs.  One version includes them within crown-group Archosauria
(in other words, they are descendants of the most recent ancestor of birds
and crocs).  In the other version, they are basal members of the
archosauriforms, but still closer to archosaurs than to lepidosaurs.

Hope this helps.