[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Underwater Flight
Rob Gay (firstname.lastname@example.org) 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
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
Where the Wind Comes Sweeping Down the Pampas!!!!
Do You Yahoo!?
Get email at your own domain with Yahoo! Mail.