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RE: Evidence For a Feathered Velociraptor...
Mike Keesey wrote:
> Or, indeed, the idea that any coelurosaur with remiges (e.g._Archaeopteryx_,
> _Microraptor_) is capable of powered flight.
> (Although we already knew that, thanks to _Caudipteryx_ and
> Powered flight seems pretty secure for
> _Ornithurae_/_Pygostylia_/_Avebrevicauda_. Beyond that, though, what
> do we really know? We have some stuff with wings, and many people assume the
> small ones flew and the big ones didn't,
> but, for all we know, _Archaeopteryx_ may not be avialan (sensu Gauthier and
> de Queiroz 2001). Or, conversely, _Avialae_
> might include most of _Maniraptora_.
I'm not at all keen on Gauthier and de Queiroz (2001)'s proposed
apomorphy-based definition of Avialae: the presence of “feathered wings... used
for powered flight.” Seriously, how are we supposed to infer powered flight
for fossil birds! Especially when the first birds had a morphology very
different to modern birds, with their long tails and puny sterna. [Personally,
I much prefer Senter's (2007) definition of Avialae, which is "all taxa more
closely related to birds than to Deinonychosauria" (cf. Aves sensu Senter, "all
taxa phylogenetically bracketed by _Archaeopteryx_ and Neornithes").]
Having said that, I agree that powered flight seems pretty secure for
Ornithurae. I also agree that the usual interpretation that taxa like
_Archaeopteryx_ and _Rahonavis_ could fly, but microraptorines couldn't, does
seem a little arbitrary. It's really difficult to compile a list of
exclusively 'flight-related' characters, given that many flight-related
characters (a) precede the origin of flight (i.e., were exapted toward powered
flight); (b) are retained in secondarily flightless taxa; or (c) evolved
independently of Aves. Characters such as the presence of quill knobs, or
asymmetrical remiges and rectrices, appear no longer to be exclusively
It is really difficult to point to a character in _Archaeopteryx_ and call it
100% flight-related. You could find the same character in a microraptorine, or
even a velociraptorine. I suspect it's the overall 'gestalt' of
_Archaeopteryx_'s morphology (both integument and skeleton) rather than
individual features that pushes it over the line. As Mike said, the size of
the critter helps, given that _Archaeopteryx_ is below the cut-off for a flying
animal (although I don't know quantitatively what the cut-off actually is),
whereas velociraptorines and basal oviraptorosaurs (_Protarchaeopteryx_,
_Caudipteryx_ are clearly too 'big', or have arms that are too short. Also,
_Archaeopteryx_ has only two wings associated with the limbs, as in modern
birds (not four as in microraptorines) which makes comparison with modern avian
> Seen that video of an eagle driving off a wolf? The eagle is (among
> other things) beating the wolf about the head with its wings.
Yes, but the eagle isn't trying to *catch* the wolf with its wings. This is
where the analogy breaks down. For dromaeosaurids (or at least dromaeosaurines
and velociraptorines) the forelimbs appear to have played a major role in
catching and subduing prey. And yet, _Velociraptor_ presumably had two
featherdusters strapped to its arms.
> Geese and swans do that as a defence, or when having disputes with one
> another; all sorts of ducks do that, too. Feathers aren't that fragile.
True. But in a battle between the beak of a desperate _Protoceratops_ and an
arm feather, I think ther feather would come out second best.
> It's also not clear that the very limited range of motion in the
> maniraptoran manus was used for holding the struggling prey at all; the
> proto-flight-stroke looks more like a mechanism for slashing something
That's a cool idea. Has it been looked at in detail (biomechanics, etc)?
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