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Re: Sickle-Clawed birds



David Marjanovic wrote:

<There is a reconstruction of Patagopteryx in The
Dinosauricon showing it as a basal alvarezsaur.
Judging by how little is known of the skeleton (e. g.
the tail is completely unknown, the arms "end" just
below the elbows), and by the fact that it was
described before Mononykus, this is possible.>

  It's not *Patagopteryx*, a bird. It's *Patagonykus*,
which is an alvarezsaur originally described in 1996,
then fully described in 1997, both by Novas. This form
has partial forelimbs including the forearm and manal
elements, and they are surprisingly large for an
alvarezsaur compared to *Mononykus* or *Shuvuuia.*
Even *Alvarezsaurus* apparently has smaller arms
relatively, though I'd have to check. The
reconstruction on Mike Keesey's Dinosauricon had
better have the forelimbs, or I'm going to be very
annoyed....

<However, T. Mike Keesey still puts it into Euornithes
and allies it with Gargantuavis and Kuszholia as
Patagopterygiformes (interesting and not implausible,
but I don't have an idea why). Sickle claws or
hyperextendable toes or whatever are said to occur in
Ornitholestes, too, so maybe that's a coelurosaurian
or neotetanuran synapomorphy lost several times.>

  *Ornitholestes* has very little of the pes
preserved,  with only partial elements of the right
pes, and some metatarsals. This is not enough to base
a suggestion of hyperextensibility. What it seems like
is that the second pedal toe bore a rather largish
claw, but the pedal ungual elements are fragmentary
anyway, and this leads to the following state
regarding any "raptorial" modifications of the pes: ?

  The qualities of the troodontid, noasaurid, and
dromaeosaurid pes (the second type is also seen in
*Rahonavis*, and *Archaeopteryx*, as in most raptorial
birds, has a very large second toe claw, compared to
the rest, but arguments towards *Archaeopteryx* having
a hyperextensible toe are based more on phylogeny than
osteology, and Wellnhofer has pretty much stated that
there is no evidence for it being "flippable" as in
dromaeosaurs, etc.) are different in quality and
ability, and are easily discernible from phalanges,
unguals, and metatarsals, from each other.

  Lastly, *Megaraptor* has a large claw that is
refered to the pes, from Novas, 1998, based on
comparison to dromaeosaurs. It may not be referrable
to the pes at all, because one of the feature
distinguishing pedal from manal claws in the raptorial
form is the shape of the flexor tubercle and features
of the proximal articular facet and overhanging
proximodorsal rim.

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

  Dinosaurs are horrible, terrible creatures! Even the
  fluffy ones, the snuggle-up-at-night-with ones. You think
  they're fun and sweet, but watch out for that stray tail
  spike! Down, gaston, down, boy! No, not on top of Momma!

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