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Combined re: Lemurs and Feathers



HP Dinogeorge wrote, in several different postings:

> In a message dated 6/19/01 4:18:14 PM EST, david.marjanovic@gmx.at writes:
>
> << except for a lack of arboreal adaptations in
>  theropods (such as mobile extremities and grasping feet) >>
>
> Grasping feet were secondarily lost in most cursorial theropods; the small
> digit I at the side/back of the foot is all that remained of the opposable
> hallux. Having a large hallux pointing backward on your foot is rather
> detrimental to fast cursoriality, so it is quickly vestigialized in such
> theropods.

Sounds logical, and has indeed happened several times in birds. But chicken
embryology runs the other way round, from a rather vestigial non-opposable
to a lengthened, lowered, opposed hallux. Ref:

David Rubilar, Alexander Vargas, and David Lemus:
The dinosaur-bird transition compared to the development of the chick
(*Gallus gallus*), SVP meeting abstracts 2000, p. 65A

I've posted the entire abstract some months ago.

> OK, then. At what stage in the development of wings for [...] swimming
> do they become exaptable for flying? And if a theropod has evolved wings
> for brooding in a terrestrial (versus arboreal) lifestyle, or for swimming
in
> an aquatic lifestyle, when does it "decide" to "try out" its brooding
wings
> for flight?

Phew, when the wings have evolved a suitable shape, and when the coelurosaur
is
small enough and has reasonably large flight muscles... A rather arbitrary
point, just like in the arboreal and cursorial scenarios. :-)

> In a message dated 6/19/01 5:02:48 PM EST, TomHopp@aol.com writes:
>
> << So far, ALL THE DATA are consistent with brooding. >>
>
> I don't see any brooding wings in Microraptor (or that new small theropod
> still unnamed). Feathers, yes. Brooding/shading wings, no.

In species that didn't use them for other things than brooding, wing
feathers may well have been a seasonal phenomenon, IMHO. So we might still
find one with wings. If not, no problem, either *Caudipteryx* or
*Archaeopteryx* is less closely related to birds than dromaeosaurs sensu
lato -- *Microraptor* might have secondarily lost its wing feathers, for
whatever IMHO improbable reason.

> In a message dated 6/19/01 5:31:47 PM EST, TomHopp@aol.com writes:
>
> << The problem with underwater flight is lack of fossil evidence. [...] >>
>
> The problem with cladistic analysis of theropods is that it misleads one
into
> thinking that the common ancestors of  theropods and birds more closely
> resembled the theropods rather than the birds. There is no reason

except parsimony

> to favor
> this viewpoint over the opposite, namely, that the common ancestors of
> theropods and birds more closely resembled birds (in appearance and
> behavior).

IMHO the first eumaniraptoran sensu meo must indeed have looked a lot like
*Archaeopteryx* (otherwise my phylogeny requires awful lots of
convergences). I just say it didn't live in trees.

> The fossil record supports neither viewpoint, or rather, either
> viewpoint equally, since it does not provide any fossils sufficiently
close
> to those common ancestors to resolve the issue. Lack of fossil evidence
> hampers >all< scenarios of the origin of avian flight.

Well, you say it :.-(