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Re: Evidence For a Feathered Velociraptor...
On 9/24/07, Tim Williams <firstname.lastname@example.org> wrote:
> 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."
Like it or not, and whatever it includes, it's a useful taxon to have
a moniker for. (And the name does mean "bird wings"....)
> [Personally, I much prefer Senter's (2007) definition of Avialae, which is
> "all taxa more closely related to birds than to Deinonychosauria"
That definition is much older than Senter (2007).
> 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,
Microraptorians (and here I thought you were following Senter's nomenclature).
> 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.
Or, better, of _Avialae_. (See, it is useful....)
> Characters such as the presence of quill knobs, or asymmetrical remiges and
> rectrices, appear no longer to be exclusively 'flight-related'.
> 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.
I suspect it's its history as "the first bird".
> 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.
But not microraptorians....
> 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 flight easier.
It does have pretty long leg feathers (although not as long as in