Re: Longisquama closer to theropods than sauropods?

["Matthew Troutman" <m_troutman@hotmail.com>]

<<In any case, since sauropods are saurischians and share a number of 
anatomical features with theropods, why do you think _Longisquama_ would be 
closer to theropods and birds than sauropods?  Would you stick _Longisquama_ 
as a sister group to theropods and birds, and if so, where would the 
Sauropodamorpha go?  Something different?  Is _Longisquama_ a  saurischian, 
then, by your definition?>>

Good points.  I think that basing a theropodian or basal saurischian 
placement on _Longisquama_ (fully acknowledging G. O.'s interesting and 
provative views on dinosaur phylogeny) on two features is stretching what we 
know.  _Longisquama_ is so incomplete that we don't know enough of it to 
gauge what possible theropod autapomorphies it may display but it is 
conversely complete enough to be provacative.  But, without even display of 
basic ornithodiran, dinosaurian features we cannot say where it falls in the 
larger scheme of things.  As I pointed out before, _Longisquama_, if we 
accept that the "furcula" is part of the interclavicle, still a speculation 
but a little better than looking at the general similiarities of its 
"feathers" and saying that it most be close to birds, could fall into the 
lepidosauromorph side of the neodiapsid tree.  The lepidosauromorph 
interclavicle is very very distinctive and it seems possible, if not 
probable, that _Longisquama_ exhibits the basic "T" shape found in most 
lepidosauromorphs if we put its "furcula" and interclavicle together .  This 
is a lot stronger evidence than anything indicating a close relationship to 
theropods and/or sauropods.

Of course this might not even mean a lepidosauromorph affinity, since some 
parareptiles exhibit it as well if I remember correctly.  It is also 
interesting to note that Evans (1984) thought that _Longisquama_ might be a 
late-surviving coeluroavisaurid and its "feathers" would be some sort of 
thoracic rib expansion, which I don't believe but is interesting to consider 
since nobody at that time thought anything other than _Longisquama_ was some 
sort of "pseudosuchian".

Matt Troutman
m_troutman@hotmail.com


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