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RE: ABSRD BAND on Sinornithosaurus feathers



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Dinogeorge@aol.com
>
> In a message dated 3/15/01 10:20:24 AM EST, kinman@hotmail.com writes:
>
> << If every stage in the
>  evolution of a morphological structure has to be adaptive, then it is
>  difficult to fathom how a simple hollow cylinder or a pine needle-like
>  branching structure can be functional in an animal. >>
>
> As usual, they overlook the obvious solution to this conundrum:
> the feathers
> of Sinosauropteryx and some of the other Liaoning theropods are
> derived from
> more birdlike feathers such as those seen in the earlier Archaeopteryx.

Actually, they are ignoring something even more fundamental, which is the
actual way feathers develop in living birds.  Prum, Brush, Maderson, Lucas,
Stettenheim, and others have done some excellent work on this subject: see,
for example,
http://www.bioone.org/bioone/?request=get-document&issn=0003-1569&volume=040
&issue=04&page=0513 (Maderson & Albardi's contribution to the SICB Feather
Symposium).  In particular, check out figure 4C.  Feathers are really a lot
weirder than you think they are in the way they grow: a strange
conveyer-belt like mechanism that adds the accessory structures onto the
main shaft during development.

The model advocated by "Cal King" in the posting Ken Kinman provided would
be analgous to suggesting that mammalian molars formed by having a conical
tooth erupt, and then be whittled down (by what? Gnomes?) to the derived
shape after the tooth has emerged from the gumline.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796