Re: Archaeopteryx not the first bird, is the earliest known (powered) flying dinosaur

[MICHAEL HABIB <habib@jhmi.edu>]

Others have already covered most of the comments I would have made, but I do 
still have a couple of thoughts on the subject at hand...

Jim brought up some excellent points regarding the expected trends regarding AR 
and wing loading in glide-adapted species.  I would add to this line of inquiry 
the observation that the planforms differ pretty significantly between 
Microraptor and Archaeopteryx (and probably Sinornithosaurus, too, but harder 
to tell).  Aspect ratios are very likely different.  Wing loadings probably 
differ as well but the body mass estimations present in the literature cover 
such a vast range it is hard to say.  In any case, it doesn't seem like 
Microraptor was just doing what Archaeopteryx was doing, only better, so to 
speak.  That being said, there are issues regarding the wing shape parameters 
in the two species that are hard to determine.  For example, Archaeopteryx may 
have been able to open slots, and thus had a higher effective AR than it seems 
to at fi
rst glance (though, judging by the relative lengths of the primaries, these 
slots would be small).

One note on the phugoid gliding model: I like some aspects of this model, but 
there are some issues with it.  Not the least of these is the fact that 
Chatterjee and Templin modeled their Arch. taking off from a launch point 15 
meters tall.  While trees of this size may have been present on the European 
islands at the time, it is somewhat troubling that none of the specimens of 
Archaeopteryx, to the best of my knowledge, were preserved in (or near) this 
forest habitat (which would have been restricted to inland areas).  Now, that 
doesn't mean they didn't live there, of course, but there is certainly a rather 
distinct absence of data problem.  This is especially troubling if 
Archaeopteryx is billed as being heavily arboreal.  It's much less of a problem 
if (as several on this thread already suggested) the animal was only 
semi-arboreal and happy in multiple habitats.  

I'm hardly
 the first to mention this disparity, but I thought it was worth bringing up 
since the phugoid gliding model was mentioned.  Unlike other gravity-powered 
gliding models, the phugoid model specifically requires a rather high launch 
point (otherwise the animal hits the ground along the way in a rather 
unfortunate manner).

As long as we're talking about modern analogs for incipient flight (somewhat 
useful, if dangerous) I would like to suggest looking at escape behavior in 
Rollandia microptera (short-winged grebes).  They cannot take off, but still 
retain the ability to generate intense bursts of speed over the surface of the 
water using their reduced wings.  It's a method of escaping predation, and it 
makes a big difference for the grebes: human hunters preferentially take the 
fully flightless coots living in the same habitat, in part because the 
sprinting grebes are just a pain to catch and kill.  

The point is not that theropods were grebe like, but simply that generating l
ift with wings has utility even if the animal cannot takeoff (much less sustain 
flight).  The point is made regularly by others, but I like the example.

Cheers,
--Mike