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Re: Underwater Flight



Rob Gay (rob_redwing@hotmail.com) wrote:

<Now, does this suppose that these theropods are already
feathered when they enter the water? Because if they aren't, I
see no pressure for them to evolve feathers, once aquatic.>

  Chatterjee has suggested that it was possible for dinosaurs to
develop feathers through a gliding phase previous to the "run to
the sea," so that feathers were already developed. As has been
demonstrated (I forget by whom, possibly Olson or Cracraft) that
penguins [like auks] stem from a lineage of fully-flighted
birds. That hesperornithiforms are basally flighted by the most
primitive forms, shows that no form is plesiomorphically
aquatic, and so feathers must have originated outside of the
pressure of a liquid environment, and in fact that a water
environment acts to decrease feathers as a motivational
structure. Foot-propelled animals (such as grebes and
hesperornithiforms) reduce pectoral anatomy, whereas penguins as
wing-propelled divers, reduce only their aspect ratio and
increase four-limb anatomy and bulk.

<Also, on the comment earlier about segnosaurs; if they were
saurapodamorphs, even with their dino-fuzz, then what
implications does this have for the origin of fuzz (is it a
basal character, like mammal fur?), and what would this mean for
BCF?>

  Segnosaurs, as the bizarrosaurs they are, are theropods,
nested within Maniraptora by the most recent analyses -- (the
biggest whopping maniraptoran is Therizinosaurus, by the way),
and statements that continue to suggest they are sauropodomorphs
or basal saurischians are exclusive of the descriptions of
*Alxasaurus* or *Beipiaosaurus*, for the most part. Discussions
on list on this subject are quite extensive, so it would be a
good idea to search "Alxasaurus" and "Beipiaosaurus" in the
archives to pull these up.

=====
Jaime A. Headden

  Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
  Where the Wind Comes Sweeping Down the Pampas!!!!

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