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RE: Cost in Aquatic Birds (the big one)
David Marjanovic wrote:
> Thanks to HP Tim Williams for anticipating some of my questions and
> thereby shortening this post. :-)
No problem. But - yikes! - how much longer would your post have been
> Positive data exists for several theories, including the Hopp and
> Orsen brooding hypothesis
> it provides the BCF hypothesis with one for why wing feathers
> and not a patagium evolved;
We don't need to invoke a brooding --> flight scenario to account for this.
Birds appear to be only the flying vertebrates that we know evolved from
bipeds. (I think it's a safe bet that bats had a quadrupedal gliding
ancestry, and this may apply to pterosaurs too - but I'm aware this is
contentious) As such, the pectoral skeleton only was available to support
the wing surface in birds. This precluded the evolution of a membrane
(patagium) linking the fore- and hindlimbs.
Besides, early birds and their forbears MIGHT have had a mini-propatagium -
though I'm aware that no fossil _Archaeopteryx_ or feathered deinonychosaur
shows a propatagium, AFAIK.
> Not to mention the behavior of adult stone"flies" (which are
> basal Pterygota).
Last I heard, Plecoptera (stoneflies) are considered basal Neoptera.
Odonata (dragonflies, damselflies), Ephemeroptera (mayflies) and a bunch of
extinct orders are basal Pterygota (winged insects). Neopterans can fold
their wings across their abdomen; non-neopteran pterygotes like dragonflies
cannot. (I majored in entomology, but it's been a while so insect taxonomy
may have changed.)
Timothy J. Williams
Iowa State University
Ames IA 50014
Phone: 515 294 9233
Fax: 515 294 3163