Re: A New Hypothesis for the Origin of Flight?

["David Marjanovic" <david.marjanovic@gmx.at>]

> HOBHY?

The Hopp & Orsen Brooding Hypothesis (wings are for shielding eggs and/or
young from heat and rain). (c) Jaime A. Headden some weeks ago.

> > Basically the same as what has recently been
> > proposed for bats. Very good, IMHO, because that
> > way you get trees-down without parachuting and
> > gliding.
>
> Can you give a brief lay-out of this hypothesis? I
> don't want to suffer under the illusion that I had an
> original concept.

I don't think I've read anything about it on paper, let alone primary
literature... well: Imagine some sorta kinda shrew running around on early
Paleocene trees. It uses its hands to catch insects and/or to reach branches
while it's leaping. When it fails a few times, when that behavior gets
repetitive, it's already flapping. Begs a question or two about where the
patagium comes from, but allows bats to evolve trees-down (or rather in the
trees) without parachuting and gliding.

> > > Even if they did manage to get a good grip,
> > > powerful muscles would be needed to pull the body
> > > onto the next branch [....]
> > Possible. But very flexible arms and hands would be
> > very advantageous here.
>
> What if both forelimbs secured a branch, and the
> animal just hoisted itself right up onto it? It really
> depends on how you climb, imho.

You mean like that mounted *Deinonychus* skeleton cast on some website
(cited in the archives)? Okay, but that way it's difficult to get from one
branch to another. And if the animal is as small as *Microraptor*, it's very
difficult to get up a tree that way.

> You can have very
> supple appendages, or stiff ones that provide more
> stability. The stiffening of the body in a number of
> avepectorans might solidify the body, reducing the
> stresses on the skeleton incurred from moving in the
> aforementioned way.

Sounds counterintuitive... could you give an example of an animal that does
that?

> Now that mention of the aye aye appears in DA, can we
> discuss it openly? GSP doesn't give it much of a
> description, but he does describe it nonetheless....

Oho!!!

> > And still, it isn't reverted except in and very
> > close to Pygostylia.
>
> While I think this will change, I don't see how it
> would impact the hypothesis....it's just another
> climbing adaptation in more derived proto-avians.

Well, at the moment it looks like that feature appeared unexpectedly late,
unexpected if all those beasties were indeed climbers, that is. I still
think arboreality came after flight in birds (but soon after).

> > if *Eshanosaurus* is indeed a segnosaur,
> > then oviraptorosaurs are at least as old as that
> > and had _plenty_ of time to reduce their halluces.)
>
> Reverted halluces snag and are damage-prone in
> runners. I'd expect them to be lost quickly.

All those terrestrial Galliformes still haven't lost or even shortened
them... okay, they're not really cursorial. But since when are there
roadrunners (reverted toes I and IV)?

> Well, new specimens are always being dug up in
> China....we probably won't have long to wait.

But I'd expect e. g. more mobile hips, knees, ankles, elbows and wrists in
those that are already known :-)