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In a message dated 96-02-28 19:40:36 EST,
T.Williams@cclru.randwick.unsw.edu.au (Tim Williams) writes:
>I read somewhere that _Sharovipteryx_ is a member of the
>Prolacertiformes i.e. a diapsid and close relative of the prolacertids
>and tanystropheids. I can't remember the author or the source
>(sorry!). I guess the pterosaur theory is passe... (at least
>according to this study).
Do not be so quick to write off a close relationship between _Sharovipteryx_
and pterosaurs. While _Sharovipteryx_ lacked the relatively huge forelimbs
and wing membranes of pterosaurs, it still had a couple of broad pterosaur
apomorphies: an uropatagial membrane (very extensive, naturally) and a large,
elongate, narrow skull. The question of whether it had an antorbital fenestra
is still open, because the only known specimen has a crushed skull in which
an AOF could have been obliterated.
Also, it is possible (according to DPterosaur and some European workers) that
pterosaurs were not archosaurs but acquired their wide AOFe (antorbital
fenestrae) independently, in descending from prolacertiform diapsids. Thus,
if _Sharovipteryx_ turns out to be a prolacertiform itself, it could still be
closely related to pterosaurs.
I'm still partial to pterosaurs as archosaurs, but I'll certainly change my
opinion if convincing evidence turns up that this is not the case.