RE: Cost in Aquatic Birds (the big one)

["Williams, Tim" <TiJaWi@agron.iastate.edu>]

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
otherwise?

> Positive data exists for several theories, including the Hopp and
> Orsen brooding hypothesis 
[snip]
> 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.)



Tim



------------------------------------------------------------ 

Timothy J. Williams 

USDA-ARS Researcher 
Agronomy Hall 
Iowa State University 
Ames IA 50014 

Phone: 515 294 9233 
Fax:   515 294 3163