Re: Noasaurids (was Re: New Sauropod from Portugal)

["Jaime A. Headden" <qilongia@yahoo.com>]

I've just come back after a long absence from the internet (a month) and I felt
I'd like to chime in on this rather old topic for a second.

  Having reconstructed *Noasaurus* and *Masiakasaurus*, I am familiar with the
issue regarding the nature of the peculiar claw. Bonaparte clearly saw allusion
in the ungual's form to that of dromaeosaurs, and since then it seems South
America has had a lonely but seeking relationship with nearly every vaguely
coelurosaurian found in its earth with large claws, finally meeting its match
with *Buitreraptor* and one hitherto undescribed specimen from Patagonia (and,
of course, opening up the possibility that *Unenlagia* is one of these
critters, too).

  Having a foot-sickle in your own backyard is a romantic idea, and it may have
clouded the otherwise potentially obvious answer that the ungual was manual in
nature. This issue occured with the discovery of "Claws", the type specimen of
*Baryonyx walkeri*, which for a while was considered to be a giant English
dromaeosaur, as well as the more well-known case of *Megaraptor*.

  However, the ungual bears no similiarity to pedal claws of any form, save for
the strongly curved dorsal margin and the extremely narrowness of the "claw"
itself from the base, with regards to dromaeosaur or troodontid unguals. It is
even less like the classical "thagomizer" in that it possesses a longitudinal
depression or channel on its ventral margin, rather than a rounded inner curve
or a tomia. It is also surprisingly small for the associated metatarsal to
represent a significant weapon of any sort, though this does not alone rule out
the nature of a pedal nature for the ungual. The peculiar lack of a distinct
flexor tubercle, however, neccessitates a consideration that the ungual was not
held in such a position as to be able to flex into a grappled object, or when
the animal would have been climbing and using the claw as a piton of sorts.
This impairs the consideration of a pedal sickle, but this weakness of the
tubercle is seen in many manual unguals of various theropods, and may easily be
explained as such. It was the discovery of the nearly complete remains of
*Masiakasaurus* pedes, albeit from many incomplete but combined specimens, that
allows replacement of the ungual away from the pes. It also allows argument
that *Velocisaurus* may represent a form of the foot of *Noasaurus*, and thus
firmly removing the ungual from a pedal identification.

  Whatever the nature of the case, I have restored the ungual as manual, and
for its size likely the pollecial or thumb claw. I have rendered the holotype
skeleton here:

http://dino.lm.com/images/display.php?id=1987

  and that of *Masiakasaurus* for comparison here:

http://dino.lm.com/images/display.php?id=3085

  Note that the latter follows some material presented at 2005's SVP
presentation, and is highly hypothetical in nature.

  Cheers,

Jaime A. Headden
http://bitestuff.blogspot.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


 
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