Re: Oviraptor wrist

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

Luis Rey wrote:

<I've been trying to find some literature about it but
couldn't find something specific:  Oviraptor wrists
must have the semi-lunate mechanism to help it fold
sideways (or wing-like) like Velociraptor. Is there a
case for a sideways folding hand as a specific
characteristic of all maniraptorans?>

  While Osborn (1924) illustrated the first
semi-lunate wrist for *Oviraptor,* followed by
Barsbold (1983) and Smith (1992: redescription of type
specimen), this feature is best exemplified in Norell
et al. (1996; 1999) in the famous brooding specimen.
But commentary aside. All major genera of Maniraptora
(Oviraptor, Deinonychus, Velociraptor, Chirostenotes,
Caudipteryx, Archaeopteryx, etc.) have semilunates
with a distinct halfmoon profile. A similar form of
the semilunate in maniraptoriform theropods includes
the compressed discoidal (but separate) bones of the
ornithomimosaurs, and the cuboid and fused form in
troodontids and tyrannosaurids (the MOR (Wankle) and
FMNH (Sue) specimens of *Tyrannosaurus rex*, to be
exact). Based on Holtz (1994; 1995; 1996) and Padian
et al. (1998) the semilunate as a folding mechanism
can be hypothesized as having developed at least by
the basal Maniraptoriformes, then was succesively
modified in ornithomimosaurians, troodontids, and
tyrannosauroids, whereas the Maniraptora retained the
halfmoon shape; or, the development of a halfmoon
semilunate is unique to the Maniraptora while a
precursor was used by other maniraptoriforms, the
ornithomimosauroiians again modifying the form; a
block-like semilunate of fused form is known, I
believe, in *Allosaurus,* so this feature may stem
back to the basal Avetheropoda [= Neotheropoda?] or
was independantly aquired in both groups, with a
progressive series _known_ in maniraptoriforms and,
specifically, maniraptorans. Of course, Aves further
modify the semilunate by fusing the metacarpals to the
distal carpals, including the semilunate, but that's
them. Additionally, the therizinosauroids also possess
a semilunate, in *Alxasaurus* and *Therizinosaurus*
(see Perle, 1976?; and Russell and Dong, 1993) which
has the halfmoon, hinged proximal surface but is
composed of two separate bones. Considering the size
of the latter specimen, while it is conceivable, it is
unlikely the animal is not an adult.

  Does this answer your question?


=====
Jaime "James" A. Headden

"Come the path that leads us to our fortune."

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