Re: Non-theropod furculae

[chris brochu <cbrochu@fmppr.fmnh.org>]

Dinogeorge@aol.com wrote:
> 
> I'm not the only person on the planet who thinks the boomerang-shaped bone in
> the L. type specimen is a furcula.

Granted.  But having seen one of the type slabs fairly closely, I don't
think it can be regarded as an unambiguous furcula.

For one thing, it is not in articulation.  I'm not even convinced it's a
derivative of the clavicles, let alone a pair of them connected at the
midline.  I am not saying it's NOT the clavicles, but it could be
several other things.

For another, despite the fact that this structure was preserved as a
mold in the specimen I saw, one can clearly see a separation between
them.  I don't read Russian, so I don't know what Sharov actually said,
but the translator stated that the bones were "conjoined," which is not
the same as fused.  Fusion, in a histological sense, implies complete
obliteration of the cartilaginous lamina between two ossifications.  (Of
course, one could argue that this represents an earlier stage of
evolution in the furcula. One could also argue that the specimen
represents an immature individual.)

Sharov also states that the teeth of the type are acrodont - this, in my
eyes, argues against an archosaurian placement, as archosaur teeth are
thecodont.  I was not able to confirm this observation.


chris


-- 
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Christopher A. Brochu
Department of Geology
Field Museum of Natural History
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