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Re: Who says dromaeosaurs can't fly?



Greg Paul (GSP1954@aol.com) wrote:
 
<Everyone get used to it. At least some basal dromaeosaurs could fly baby,
and better than Archaeopteryx. In no way was Crypto a protoflier, it was a
fully developed flier whose performance approached and equalled that of
pterosaurs and confusiusornithids that lack deep keeled sterna but have
well developed wings. The dromaeosaur should have been able to take off
from level ground, climb and fly a substantial distance, and land high in
a try. It may have used flight as a regular attack mode. Imagine
sickle-claws perched high in trees, waiting for some hapless prey to walk
through the neighboring glade only to be pounced upon from above!
Screaming dinosaurs from the air! (Research into stomach contents
indicates that cladists were considered especially tasty). Since the Jehol
is churning out fossils like candy out of a Hershey factory we will get
more and more fossils that will only make this increasingly clear, so
there is no point making a fuss about it. You don't want to be like those
who went on and on about how dinos don't have feathers and those fibers
are really just frayed collagon, now do you? If you do, the burden is upon
you to demonstrate that Cryptovolans was not a competent flier.

 Readjust your minds to the new reality.>

  I'd hate to think what this statement may imply, on the nature of people
trying to _not_ accept volant dromaeosaurids. The converse is true, as
made from statements on this list. Some individuals appear to think the
multitude of us are arranged against the "truth."

  However, before we get screwed up on this, recall that we are dealing
with different clades of animals, though Paul prefers his stem-based taxa;
the clades that define the separations of clades are not so broad as his
stems. The group of dinosaurs to include both birds and dromaeosaurs is,
by use and definition, Eumaniraptora. Basal eumaniraptorans have long
arms, "fluffy" integument, robust manus, and large claws. They are also,
contrary to some opinions, apparently derived in the terrestrial system.
Other than artifact through ancestry, the metatarsus is elongated and
designed with a pinched-out third metatarsal, a mechanic demonstrated
(Holtz, 1995; Paul, 2000), to be a _running_ adaptation.
Non-eumaniraptorans, like oviraptorosaurs, *Ornitholestes*, etc., lack
these features, as well as several basicranial adaptations, that set them
apart. Integument are filamentous in nature, and fully pinnaceous and
possibly barbulated feathers are known in an acknowledged basal
oviraptorosaur. Most derived dromaeosaurs and troodontids have pedal claws
with shallower recurvature, and a heterodactyle pes (all toes forward).
They also have short arms, compared to trunk length, and a nearly vertical
proximal pubis. Nothing shows *Microraptor* was opisthopubic, and
comparison to *Sinornithosaurus* suggests it likely was not. *Sinovenator*
is opisthopubic, and strangely enough it's pelvis is more similar to
*Archaeopteryx* and *Velociraptor* than are basal dromies and *Rahonavis*.
Recent analyses place *Unenlagia* within Deinonychosauria, and even Paul
(2001) precludes a initial trend in reduction and degeneration of flight
in Deinonychosauria, rather than trending towards flying.

  Direction is not really important, but it seems to be on everyone's
mind. I wonder why.

  The basal fellows, like *Sinovenator*, *Microraptor*, and
*Sinornithosaurus*, have large arms, large shoulders with reflexed
coracoids, and large sterna. What they do not have are true pinnate
feathers. From the photos I've seen of *Cryptovolans*, the feathers lack
barbules, and would not have been very aerodynamic in this feature. The
opposite is true of *Archaeopteryx* which also has a more derived
shoulder, longer arms, and mechanic of the wrist and shoulder that conform
to an elevator system not seen in *Cryptovolans*, though admittedly I must
look again when I get a hold of the volume.

  The argument that any vaguely dromie animal is a dromaeosaur must depend
on some sort of phylogenetic concept for the word/term "dromaeosaur"; if
in generalities *Cryptovolans* is a "dromie," then fine, but it is not a
dromaeosaurid (member of clade Dromaeosauridae), I can assure you. And in
an argument such as this, semantics is king. You _must_ argue the
particulars and not the generalities to assess the nature of something or
an approximation of it. Flight is a biomechanical issue, not a typological
one, and assessing an animals flight performance by feather type, size,
mass, and arm size, means nothing, in this respect; it has to be
demonstrated the mechanisms under which flight can be acheived, and the
dynamics to which feathers and therefore a wing can perform
aerodynamically. An ostrich has long arm feathers, as do "weak" fliers
like tinamous, woodcocks, and kagus. The emu has the most mechanically
"wing-like" arm structure of any ratites, and proportionately the longest
wings, but as a ratite it is fairly advanced compared to the moa-kiwi
clade, which have virtually no arm skeleton. The effects of paedomorphosis
have been invoked for some aspects of paleognath and neognath evolution,
but they have not been strongly applied to the origin of flight; indeed,
until the "Farlow and the dark side" paper on *Caudipteryx* and limb
proportions with Terry Jones et al., the question of paedomorphosis in the
evolution of the avian hindlimb has not been broached strongly, and is an
aspect that some researchers are exploring ...

  ... but we ain't there yet, folks. Nothing stops us from speculating,
but nothing _is_, and especially with paleontology, "there are no
absolutes."

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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