[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Origin of feathers



In a message dated 98-05-04 19:35:04 EDT, jaemei@hotmail.com writes:

<< Name me a bird that broods with feathers on the 
 lateral surface of the body. While not disparaging the idea that yes, 
 the brooder could have had brooding feathers on the sides, it is not 
 unpresumptuous to say that yes, there could have been brachial feathers 
 long enough to brood with, and even not interfere with the other manual 
 or brachial motions of the arms. >>

You're missing my point here. I would assert that there are no lateral
brooding-feathers in birds because they make use of the feathers that appeared
on their forelimbs for reasons other than brooding. When you assert that
feathers appeared in birds >for brooding eggs<, you haven't explained why they
would appear preferentially on the forelimbs and not somewhere else, such as
the sides of the bird or the back, etc. You need to come up with something
about the forelimbs that would compel the evolution specifically of brooding-
feathers there, to the exclusion of other parts of the body.

<< Many birds can adjust their feathers so they do not stick out, lay 
 flat, etc. The ventral surface of the avian ulna is ridged, while 
 *Oviraptor*'s (for instance) is not, and we already assume Archie could 
 use his claws and fly (or ornithopt, or whatever). The ridge actually 
 stiffens the quills, while a rounded surface would not provide any 
 direct anchor for the ends. Thus, we can assume that a brooding dinosaur 
 could actually tuck its feathers parallel to the arm, and never 
 interfere with the manual motions. >>

This is actually a pretty strong argument against the existence of >any<
sizable wing feathers on the forelimbs of _Oviraptor_. Perhaps we should
consider whether _Oviraptor_ retained any feathers at all, let alone elongate
brooding-feathers of some kind. Perhaps _Sinosauropteryx_ fuzz is all the
feathers _Oviraptor_ had, too.

<< The hallux is for perching or even grasping while the foot is off the 
 ground.
 
   How does the bird get to the branch to perch (and why?) unless by 
 climbing or by flight. Like a woodpecker, climbing is made easier by 
 using a stiffened tail for balance, and the fourth toe is retroverted to 
 make maximum gripping ability on the vertical surface. Whether Archie 
 used his tail to help him climb up to gain an advantage point from which 
 to launch off is considerable [something to consider].  >>

And what do these things have to do with brooding? We're looking at brooding
as the raison d'etre for wing feathers in flightless theropods.

(Not that I disagree with this notion of a stiffened tail as being useful for
balance.)