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Re: origin of bats/reply 2 to TMK



Alternatively, the phalanx proportions in Archie almost certainly
also allowed the digits to perform an aerodynamic function analogous to that performed by the alula in more derived birds.<<

Almost certainly? In an organism that doesn't even preserve evidence of feathers on the thumb??? I'm not denying it's possible, but that's a pretty strong statement considering the lack of evidence.

If Archie flew from tree to tree, as I suspect, extending the manus
digits during the high AOA phase necessary when approaching a target tree trunk would have aided in avoiding stall and placed the manus claws in the proper position for grasping the tree trunk upon contact. <<

And here, IMO, is the problem. You are assuming apriori that archie a) flew, and b) was arboreal. The former is debatable but a reasonable stance, the latter is entirely without merit. Archie has basically no characters associated with arboreality (its environment even seems to lack trees) and in fact had several characters that would make it worse in trees than less derived maniraptorans (notably the hind limb proportions).

If you assume that archie landed in trees, then it sure seems like it had _better_ have an alula, but none of the specimens preserve evidence of such. That could be an artifact of preservation, but not having an alula would be consistent with the lack of a reversed hallux, the short length of the hallux, the lack of strong felxor tubercles on the pes claws, the long non-sprawling hindlimbs, the lack of pectoral musculature needed to generate the force needed to oppose momentum during decceleration (p = mv) and the lack of proper shoulder stabilization should such a maneuver be attempted. Not even getting into the lack of a complete wing, etc.

It may be that an arboreal component played a prominent roll in the evolution of avian flight, but if so Archaeopteryx was not involved.



Scott Hartman
Science Director
Wyoming Dinosaur Center
110 Carter Ranch Rd.
Thermopolis, WY 82443
(800) 455-3466 ext. 230
Cell: (307) 921-8333

www.skeletaldrawing.com


-----Original Message----- From: ptnorton <ptnorton@suscom-maine.net> To: david.marjanovic@gmx.at; DML <dinosaur@usc.edu> Sent: Sun, 22 Jun 2008 6:46 am Subject: Re: origin of bats/reply 2 to TMK


----- Original Message ----- From: "David Marjanovic" <david.marjanovic@gmx.at>Â
To: "DML" <dinosaur@usc.edu>Â
Sent: Sunday, June 22, 2008 8:23 AMÂ
Subject: Re: origin of bats/reply 2 to TMKÂ
Â
Though let me quibble with a few details: Archie doesn't have longer
> fingers than *Velociraptor* and clearly still used them for grasping
(judging from phalanx proportions, claw size, claw shape).Â
Â
Alternatively, the phalanx proportions in Archie almost certainly also allowed the digits to perform an aerodynamic function analogous to that performed by the alula in more derived birds. If Archie flew from tree to tree, as I suspect, extending the manus digits during the high AOA phase necessary when approaching a target tree trunk would have aided in avoiding stall and placed the manus claws in the proper position for grasping the tree trunk upon contact.Â
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PTJN Â