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Re: flying Archie
Mike Keesey wrote:
Why does selective pressure need to be invoked? This is the earliest known
winged theropod, and it's probably not too far removed, chronologically,
from the very first ones. Long tails are just the ancestral state--perhaps
there had not been enough time to "evolve out of them".
(1) There was "enough time" for the line leading to_Archaeopteryx_ to evolve
a thoroughly modern plumage. The evolution of the integument occurred a lot
faster than that of the skeleton. One possible explanation (hypothesis) is
that selection favored the retention of the coelurosaurian body plan in the
line leading to _Archaeopteryx_ (and beyond - see (2)). If _Archaeopteryx_
had been found without feathers, I'm pretty sure that nobody would have
recognized it as a bird (something Ostrom frequently drew attention to).
(2) Long tails (by avian standards) persisted beyond the Late Jurassic, and
are even kept by at least one Late Cretaceous bird: _Rahonavis_. This tells
me that some avian lineages were in no hurry to shorten the tail, meaning
that there was an advantage in retaining a long tail - such as for their
*particular* aerial locomotor style.
(And, actually, _Archaeopteryx_' tail is rather reduced compared to
other theropods of the time.)
But not compared to some other later theropods that (based on most current
analyses) are more distantly related to modern birds - including
oviraptorosaurs and therizinosaurs. Late Jurassic oviraptoriforms may have
had shorter tails than _Archaeopteryx_ - we just don't have enough material
from these critters to know their overall proportions.