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Re: Paleo Find ("Millennium Man")



HP Steve Brusatte wrote:

> >        *Microraptor* is significant, mainly because of its size, but I
> >don't think it was any more arboreal than a cat, probably much less. Like
> >all other dinosaurs (save a few specialized birds), it couldn't sprawl
its
> >legs, for instance. IMHO, birds only became arboreal after they were
capable
> >of flying at Pygostylia level. I don't support the cursorial hypothesis,
> >either; more in my paper :.-( ...
>
> Flight evolving neither from the trees or from the ground??

Er... through the water. Sounds like pseudoscience or like the hardly
supported hypothesis that humans had semiaquatic ancestors, but it is better
than both. I got the idea from

Klaus Ebel: On the origin of flight in *Archaeopteryx* and in pterosaurs, N.
Jb. Geol. Paläont. Abh. 202(3), 269 -- 285.

This article has a few weaknesses, but I think I have "debugged" them (e. g.
I include HP Tom Hopp's hypothesis that wing feathers evolved for brooding),
and I have included a phylogeny. I'm going to tell you everything once it is
published... :.-(

> Wow, I'll have to get my hands on this paper.  When is it coming out, and
in what journal?

In theory it is coming out right now or has already. I don't know about
reality (snail-mail deserves its name on this continent). Anyway: The
Dinosaur Society Quarterly, special issue on feathers AFAIK. This Dinosaur
Society is the surviving UK branch. "£2, free to members". The headline is
"Is *Archaeopteryx* really a bird?"

> BTW, I've always regarded the arboreal hypothesis as more plausible.
Maybe Microraptor will help prove this...although it > likely didn't really
live in trees.

The arboreal hypothesis has a few big problems. One is the transition from
parachuter to glider (not actually necessary) and the transition from glider
to flyer (necessary). Why don't birds have ordinary patagia? Pterosaurs had
hair (or was it dinofuzz???) and developed patagia instead of wing feathers.

and HP Patrick Norton wrote:

> >IMHO, birds only became arboreal after they were capable of flying<
>
> Maybe we need a better working definition of arboreal. Bird species spend
> varying amount of time in trees--some of them spend no time in trees---so
> I'm not sure it's accurate to label birds, in general, as arboreal.  I'm
not
> even sure it's possible to name a single bird species that meets a strict
> definition of arboreal.

OK: "IMHO, no birds became arboreal before they were capable of flying...",
or "IMHO, the arboreal hypothesis is 100 % wrong; first birds learnt to fly,
then some became arboreal, and not vice versa". :-)

> >birds only became arboreal after they were capable of flying at
Pygostylia
> level.<

What does "flying at the Pygostylia level" mean?

Flying as well as confuciusornithids. *Archaeopteryx* (and *Rahonavis*, for
that matter) were less well adapted to flying, since they kept their long
tails. Such a tail is perfect for a bipedal animal, as it keeps the center
of gravity at the hips; flyers need it at the shoulders, at the center of
lift. *A.* was forced to flap constantly when in air, it could not glide,
because then it would have toppled over (contra lots of people).