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RE: Avian Monophyly (Was Re: Sheesh)... :-)
Evelyn Sobielski wrote:
I don't really see a major problem though - Archie was certainly not a
specialized percher, it has >been rather well-supported for long.
Yes, true. I would even go a little further and say that Archie couldn't
perch at all. That's not to say that it wasn't arboreal, though.
I think this alleged non-monophyly of Aves is a storm in a teacup. The
Science paper by Mayr et al. (2005) implies that the monophyly of Aves is
challenged if _Confuciusornis_ is shown to be closer to traditional
non-avian taxa (like dromaeosaurids) than to _Archaeopteryx_. But Aves, by
definition, is monophyletic. All that happens under the proposed cladogram
is that some additional taxa (dromaeosaurids & troodontids) get scooped up
into Aves, which in turn suggests that secondary loss of flight occurred in
certain taxa close to the base of the Aves.
A future analysis may recover a different topology, such as an 'orthodox'
_Archaeopteryx_-_Rahonavis_-_Confuciusornis_ clade that excludes
deinonychosaurs. As has been noted previously, non-basal avians are
conspicuous by their absence from Mayr &c's analysis, and this is sure to
have an effect on the result.
(I don't think it was a dedicated ground critter either. Everything seems
to say mainly arboreal, good climber, facultatively terrestrial).
I'd say Archie was facultatively arboreal and mainly terrestrial. Of
course, in terms of the requisite adaptations, this may be a distinction
without a difference. :-)
The third alternative to the "Caudipteryx bird" and "Caudipteryx non-bird"
scenarios (the most celebrated case as it would be interpreted according to
either) is that the basal exaptations to "birdish" flight - gliding,
downstroke-assisted, four-winged, two-winged, but in any case utilizing
"bird" feathers - was there, just as the ability to develop a
hyperextensible TII with little evolutionary effort, feathers, the works.
I don't know if I'm understanding you correctly (so apologies in advance)
but my 'take' on _Caudipteryx_ is that its 'advanced' bird-like plumage is
the product of an ancestry from among gliding (or parachuting)
maniraptorans, and that _Caudipteryx_ itself spent all of its time on the
ground and did not glide.
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