RE: Ornithomimus had feathers and "display" winglike forelimbs

[Jaime Headden <qi_leong@hotmail.com>]

quoting Zelenitzy et al., Tim Williams writes:

<"But it is important to remember that the vanes are also the critical 
air-trapping surfaces of the insulating contour feather, as well as the lifting 
surfaces of the remiges. Moreover, the rigid shaft provides the necessary 
leverage for the feather muscles to fluff or compress the plumage. In other 
words, the basic design of (modern) contour feathers is equally suited for 
over-lapping layers of adjustable, air-trapping insulators and semi-rigid, 
light-weight, flight surfaces. The flight feathers are merely greatly enlarged 
contour feathers-enlarged for the secondary purpose of flight. Those properties 
that make them ideal insulating structures preadapted them as ideal aerodynamic 
structures."

However, if large and pennaceous forelimb feathers were originally used for 
brooding as "air-trapping insulators", then the shift to a flight-related 
function would be simpler. All that's needed is for the vane to become 
asymmetrical.

The presence of long forelimb feathers might also explain the appearance of the 
semilunate carpal wrist (which appears to have evolved *after* 
ornithomimosaurs): It was simply to help fold the forelimbs, and get the 
pennibrachia out of the way when they weren't in active use. No need for a 
flight-related explanation, or a predation-related one.>

  Is there going to have to be another paper so that people will recall there 
was an hypothesis by Tom Hopp and Mark Orsen (published recently in _Feathered 
Dragons_, mind you) on the functional antecedent role of brooding for many 
features of the forelimb and arrangement and shape of brachial feathers? It's 
not like there's a pdf of this thing floating around:

http://thomas-hopp.com/pdf/DinoBrooding.pdf

or that Thomas Hopp has his own blog on the topic:

http://thomas-hopp.com/blog/2011/09/17/more-brooding-dinosaurs/

  But it seems that hypothesis gets little remarked upon, even when ostensibly 
knowledgeable people start plugging some of its arguments in the pages of 
_Science_: Zelenitzy et al. _do not_ cite this work, despite mentioning 
"brooding."

Cheers,

  Jaime A. Headden
  The Bite Stuff (site v2)
  http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)


----------------------------------------
> Date: Fri, 26 Oct 2012 16:09:30 +1100
> From: tijawi@gmail.com
> To: dinosaur@usc.edu
> Subject: Re: Ornithomimus had feathers and "display" winglike forelimbs
>
> > Darla K. Zelenitsky, François Therrien, Gregory M. Erickson,
> > Christopher L. DeBuhr, Yoshitsugu Kobayashi, David A. Eberth, and
> > Frank Hadfield (2012)
> > Feathered Non-Avian Dinosaurs from North America Provide Insight into
> > Wing Origins.
>
>
> If all ornithomimosaurs had these big feathers on their forelimbs...
> how long would the feathers on a _Deinocheirus_ be??
>
>
> Anyway, Zelenitsky &c assign a non-aerodynamic function to the
> evolution of pennibrachia, arguing that the wing-like structures of
> _Ornithomimus_ would have been used for "reproductive activities (such
> as courtship, display, and brooding) and were only later, among
> maniraptorans, coopted for other roles, including flight." Makes
> sense.
>
>
> In that light, it is possible that a function in brooding actually
> fostered the development of vaned, bipinnate feathers that were
> superficially aerodynamic. John Ostrom in his _The Quarterly Review
> of Biology_ essay (1974) argued that the same properties that made
> pennaceous feathers suitable for flight also made them suitable for
> insulation:
>

>
>
>
>
> Cheers
>
> Tim