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Re: Rahonavis....a Bird?....a Dino?
I had got the impression from somewhere that the Raho. was considered
close(r) to droms. I wonder how that happened.
--Original Message--From: Thomas R. Holtz, Jr. : Wednesday, February 24,
1999 01:51 PM
>>1) Neither of the two flying forms is descended from the other, so either
>>flight must have evolved twice or they must have descended from a flying
>>common ancestor. The latter would make the similarity between Rahonavis
and >>droms difficult to reconcile with BAMM.
>No it wouldn't, not by a long shot! It WOULD strongly support
>dromaeosaurids being the sister group to a _Raho._ + (Archie + later birds)
>or Archie + (_Raho._ + later birds) clade, and it would certainly support a
>sickle claw being ancestral to the bird condition if the former option were
>true, but it is fully compatible with the 'standard model'.
So the large breastplate evolved twice, or was evolved in the flightless
droms, while remaining (or being) shrunk in the flying Archae. Hmm...
>Heck, if you think people are still on an "ancestor hunt", join the latter
>third of the 20th Century!
I'm just looking for the right phylogeny; if we've excluded common ancestry
(which was option 1) there only remains some kind of direct ancestry - which
wouldn't particularly embarrass me. It may be less likely than shared
ancestry, but in large types or where crucial developments are involved,
it's not so unlikely (as I mentioned in one of my recent posts which no-one
replied to). And close-to-direct ancestry is worth considering too.
In replying to Larry Febo:
>Okay, even given the premise that 'dromaeosaurids' ARE _Rahonavis_'s
>ancestors, why COULDN'T _Archaeopteryx_ also be a descendant?
Apart from the very odd breastplate reversal that would be required (see
above), and the fact that this would make Archae the only flying bird that
had moved its pubis forward, it would require Archae to have lost a feature
(uncinate processes) that have been conserved by 99.95% of all birds that
had them in their ancestry, volant or flightless. Three "bet-your-shirt"
flight features - probably trap-door developments too.