Re: origin of bats/reply 2 to TMK

[ptnorton <ptnorton@suscom-maine.net>]

> I apologize, I must not be making myself clear.  I don't consider there
to be overwhelming evidence for the flightless archie hypothesis, hence
"it may well have flown".  These is similarly a lack of overwhemling
evidence that archie did fly (and the gap between the evidence and
general perception is far larger here), so I consider it an open
question.  It is specifically this cavernous chasm between the data
for/against flight in archie and the general perception that archie
"certainly must have flown" that makes me feel it necessary to be the
voice of dissent.  It is perfectly in question as to whether or not
archie flew, and people need to spend more time doing the ground work
to establish if it flew, and if so how, before we start speculating as
to what types of selective pressures may have lead to that style of
flight.<

I think I generally agree, except that I see the evidence as already 
pointing convincingly towards some rudimentary type of flight capability in 
Archie than you might accept. I don't see the "cavernous chasm" you do. I 
think Mayr's 2005 paper on the Thermopolis specimen is a key piece of 
research not just in terms of supporting previous work pointing to a 
cursorial theropod ancestry for Archie, but also in raising questions about 
*limitations* on the extent of its powered flapping flight and about its 
adaptations to arboreality. Having said that, the overall body of the 
research on Archie, to me anyway, points to a creature that flew (defined as 
powered flapping flight) with at least a downward lift stroke, was 
functionally cursorial and was at least a facultatively arboreal. Once 
pre-avian cursorial maniraptorans reached the stage of evolving a 
thrust-producing flight stroke, I don't see how you could keep them out of 
the trees, given the advantages trees offer in terms of evading ground 
predators, opening new niches for predation and even nesting, just to 
mention a few.

I apologize about the misundertanding earlier about the alula. My point on 
that was that the selective pressures acting on the development of 
vertebrate flight, even in its nacsent stages, would be very strong for 
those physical characteristics of the airfoil that contributed to enhanced 
control at low airspeeds. As anyone who has flown a plane knows, landing is 
much trickier than taking off. My view for a long time (see many earlier 
posts on this by me, and others) has been that the exposed manus claws of 
early birds such as Archie were capable of being used in a way that was 
*functionally analogous* to the feathered alula that evolved in later, more 
derived forms.

PTJN