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Re: Lemurs and Feathers



> Dinogeorge@aol.com wrote:
>
> >Why not simply have the animal evolve a
> >rudimentary wing from a feathered forelimb that helps it to negotiate >in
> >an
> >arboreal lifestyle, and then have these selfsame wings gradually
>improve,
> >until they're capable of sustained flight? These wings could >easily be
> >exapted for brooding, underwater swimming, whatever you like, >at any
stage
> >of the scenario, as many times as you like.
>
> I have to agree with George here.  I think exaptation of feathers (from
> insulation --> aid in aerodynamic locomotion) is fine.  But wings, even at
> their primordial (sifaka-like?) stage, probably served an aerodynamic
> function from start to finish.

This implies that the condition in the cf. *Sinornithosaurus* specimen is
basal. If either *Archaeopteryx* or *Caudipteryx* is closer to Pygostylia
than this one, then it either isn't the basal condition, or wing feathers
have evolved twice.
What about the wings of *Longipteryx* that look so similar to this? Artifact
of preservation? Preservation of ~contour feathers during moulting?

> David Marjanovic wrote:
>
> >[snip] except for a lack of arboreal adaptations in
> >theropods (such as mobile extremities and grasping feet);
>
> This has come up before.  Many features in small theropods pre-adapted
them
> to the ability to climb trees - large hands; long, flexible fingers;
> inward-facing palms;

Inflexible arms. Compare yourself -- you can reach any place on your body
with all your fingers -- to any described dinosaur, living or extinct.
Inflexible legs -- inability to sprawl, the knees and ankles built as simple
hinges...

> trenchant claws...

True off the top of my head, but not sufficient alone...

> the retroverted pubis of
> dromaeosaurs, perhaps.

Perhaps, but *Unenlagia*, *Achillobator* and, more importantly,
*Archaeopteryx* don't have it. BTW, the pubes of basal ornithothoracines
like *Sinornis* are retroverted, but not as far as in ornithischians and
segnosaurs.

> Remember, many modern animals (woodpeckers, tree shrews) can climb trees
> without the benefit of specialized scansorial claws.

Tree shrews have AFAIK mobile extremities, as expected, and are small; I
don't know about their claws. Woodpeckers, however, have _specialized_ feet
(zygodactyl!!!) that have relatively big claws and are very strong, so that
they can _walk_ up tree trunks. No described non-pygostylian dinosaur -- I'm
looking forward to HP Tracy Ford's work -- has even the long retroverted big
toe of *Sinornis* or at least *Confuciusornis*.

> Heck, even goats and
> certain turtles can climb trees!

I don't even say that no non-pygostylian dinosaur could get up a tree in
principle. I just say that no described one can be called arboreal (goats
are subcursorial, and turtles... graviportal?; you won't find either moving
from tree to tree in the crown layer, say).