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At 3:04 PM 96.9.30 -0400, Nick Longrich wrote:
>Does anyone else see an obvious problem here? If Archaeopteryx had
>body feathers and they didn't preserve except in rare cases, why on earth
>should we expect to find them on Compsognathus?
No, what I am saying is that the evidence (albeit negative evidence and
from a pathetic statistical sample size) shows that Archaeopteryx and
Compsognathus did not have body contour feathers. Most people believe
because Archae is a "bird" it must have had a feathered body. All I am
pointing out is that there is no evidence for that hypothesis. When we
have a rigourous sample size then it could be decided one way or the other
but for the moment theory must follow fact. I should also point out that
there is no difference in the preservation potential of contour feathers
(contour feathers are comprised of 2 types - those of the body and modified
-only morphologically- ones which are the flight feathers of the wing.
there is no difference in either structure or composition). Therefore if
the specimen is preserving these 'wing feathers' it should preserve those
on the body as well. The only plausible explanation from a taphonomic point
of view is that they weren't there to preserve in the first place.
>How does the record of Mesozoic mammal fur compare? I can't think
>of a single example, yet I've never heard anybody refer to the idea of
>furry multituberculates or hairy primitive placentals as "rot".
Different question entirely. Mammalian hair is comprised of alpha keratin
and is very readily decompsed in nature by various enzymes and microfloras.
Feathers are beta keratin and incredibly recalcitrant (just ask why the
poultry industry spends millions in trying to develop an enzyme or
bacterium which can decompose the feather waste from a battery hen farm!).
Hence why mammalian hair is not readily preserved (and feathers are) in the
fossil record - I can think of only 4 examples ( I am sure there are a few
more and somebody no doubt will enlighten me) these are the Eocene deposits
of Messel and Geisental in Germany and Mammoths in Permafrost (Russia) and
Sloths in Caves (S. America). In theses instances the preservation is due
to very unusual circumstances namely palaeophotograph by bacteria,
replacemnet by silica on a molecular level, deep freezing, and dessication
in an antibiotic environment.
Of course you make an important point though, in that we presume that
mesozoic mammal were furry because they are mammals and after all what are
mammals but cute little furry things. In fact we don't have the evidence to
assume this but it is taken as fact by everyone -a sort of implication by
negative fact. But why stop there - why not assume one step further and
say that theraspids were furry again there is no evidence either way (maybe
evidence from metabolism may hint at it but can't prove it).
The important thing is to remain open to all hypothesis (a criterion of
being a scientist I guess) and not to disregard evidence because it doesn't
fit with particular beliefs.
And so ends PG's sermon for the day
Dr. Paul G. Davis
Division of Vertebrate Palaeontology, National Science Museum, 3-23-1
Hyakunin-cho, Shinjuku-ku, Tokyo 169, Japan.
Tel + 81 3 3364 2311
Fax. + 81 3 3364 7104