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> To: "DML" <dinosaur@usc.edu> Sent: Sunday, June
22, 2008 8:23 AM Subject: Re: origin of bats/reply 2 to TMK
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).
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.
PTJN