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Re: origin of bats/reply 2 to TMK



David Marjanovic (david.marjanovic@gmx.at) wrote:

<No. I'm saying I expect there to be a weak correlation, composed of a  
correlation between presence of quill knobs and forces on the wing feathers, 
and another between those forces and the length of the wing feathers. It may 
well be that other factors than the length have a much larger impact on the 
forces -- well, obviously, a powered flier will almost inevitably experience 
much greater forces on its wing feathers than a flightless animal with equally 
long wing feathers will...>

  Turner et al.s paper on the *Velociraptor* with quill knobs (2007, Science 
317[5845], pg. 1721, available free here: 
http://www.sciencemag.org/cgi/content/full/317/5845/1721) has the following 
statement:

  "An examination of the living families of birds shows a significant 
correlation between the absence of ulnar papillae and the loss and/or reduction 
in volancy, even though some strong flyers lack papillae (7). This raises the 
possibility that ulnar papillar reduction or absence in large-bodied derived 
dromaeosaurids reflects loss of aerodynamic capabilities from the clade's 
ancestral members. Quill knobs in *Velociraptor* could reflect retention of 
feathers from smaller possibly volant ancestors, but such feathers may have had 
other functions. Although thermoregulatory effects of secondaries on the ulna 
would be negligible, such feathers could have been used for display (1), in 
shielding nests for thermal control (8), or for creating negative lift during 
incline running (9). Whether this feature represents retention of an ancestral 
function or the cooption for other purposes, the presence of quilled feathers 
on the posterior of the arms in a
 medium-sized derived, clearly nonvolant dromaeosaur can now be established."

  1. M. A. Norell, X. Xu, Annu. Rev. Earth Planet. Sci. 33, 277 (2005).
  7. Materials and methods are available on Science Online.
  8. T. P. Hopp, M. J. Oren, in Feathered Dinosaurs, P. J. Currie, E. B.
     Koppelhus, M. A. Shugar, J. L. Wright, Eds. (Indiana Univ. Press,
     Bloomington, IL, 2004), pp. 234â250.
  9. K. P. Dial, Science 299, 402 (2003).

  I would venture to state that quill knobs on an animal with a clearly 
insufficient wing structure (and from the looks of it, the inability to raise 
its humerus horizontally level to the perpendicular, may retard some of these 
aerodynamic forces. That this animal possesses such derived features (and some 
*Velociraptor* specimens do not) is further underscored by a statement in the 
results of the materials and methods in the supplemental information of the 
above paper:

  "The absence of quill knobs in several strong flyers such as the swift 
*Apodus*, the hummingbird *Glaucis*, the parrots *Amazona* and *Melopsittacus*, 
and the albatross *Diomedea* indicate that other factors such as perhaps body 
size, wing shape, or flight styles may also affect the presence or absence of 
quill knobs in birds[.]"

  So while this tells us that Vel had feathers, it does not tell us it had 
wings. Unless we use a definition of wing to indicate anything that sticks out 
with feathers attached to it, which should therefore be true of *Microraptor*'s 
feet, and the tails of a good variety of fossil taxa like *Caudipteryx*. In 
which case, they were 3- to 5-winged animals, not 4-winged.

  Cheers,