Re: pteros have lift-off

[Graydon <oak@uniserve.com>]

On Sat, Jan 17, 2009 at 07:32:21AM -0600, David Peters scripsit:
>> And mostly irrelevant to pterosaurs.
>
> Maybe not. That's what we're trying to understand here. Pterosaurs came 
> from a lineage of hind limb leapers.

And you come from a line of scansorial hind limb leapers and
brachiators.

You can't do either, probably; some really fit humans can brachiate
almost-sort of. Nobody can do the branch-leaping of our primate
relatives and ancestors because we've exapted our feet.

You're a plantigrade, graviportal, obligate biped with substantial
cursorial adaptations.  The change happened very quickly, and good
intermediate fossils are not known, despite the change having occurred in
recent geological time, within the last 10 MYears or so.

There is no reason to suppose that the you are necessarily correct in
your expectations about pterosaur ancestry, *or* that any intermediate
fossils will ever be found, 200 Myears ago or more.  Some tithe (and oh
how I bet the pterosaur workers wish it *was* the 10% of a tithe!) of
the derived forms exist as fossils.

Jim and Mike and others are trying to figure out how the derived forms
work.  Saying those forms really ought to be constrained by their
putative ancestry is remarkably similar to insisting that because the
Wright flyer had forward control surfaces, a 747 really ought to have
forward control surfaces, too, and reconstructions that put the tail
surfaces maximally aft must be wrong.

A hundred and fifty million years is a really long time; a hundred and
fifty million years gone, pretty much everything mammalian looked like
some kind of tree shrew.  There is absolutely no reason to suppose that
the very highly derived forms being studied retain anything in the way
of the pre-volant ancestral condition in their approach to flight.

-- Graydon