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Flighty Equations



Eric Lurio wrote:

<The defintion of "mammal" has changed in the last
decade or so. How do you know that a live Olyagopolis
would look like a reptile?>

  I assume you mean *Oligokyphus,* a tritylodont
mammaliform. Mammalia is defined as a crown group, and
as such only includes those forms bracketed by extant
taxa: monotremes, marsupials, and placentals. Similar
forms, like Tritylodontoidea, Morganucodonta, etc. are
not mammals in the strictest sense (above). Question
of whether these animals may have looked like mammals
was raised on the list almost two years ago ...
keyword "Morganucodon" will be a tremendous help,
since the threads focused on it.

<As to the former comment, I'm pretty sure that's
right. Postosucius, has a theropod-like skull, but not
a theropod-like body.>

  Gosh, Chatterjee dissagreed, but.... *Postosuchus*,
a rauisuchian, does not have a theropod-like skull, it
is quite different, and involves many features of the
temporal and cranial roof anatomy that make this
animal quite different. Similarly, the superficial
appearance of a skull or body does not a relationship
make. Details, details, these are the fruits of our
lives.

<The problem is that you've got this thing sitting
there.>

  Yes, but _what_ it is does not stem from superfical
characterizations and refutable hypotheses on function
or nature of particular anatomy. Feathers, on the
table, are pinnaceous structures having barbs, vanes,
and a detailed rachis (shaft). Interestingly, Zhou and
Wang (2000) describing a new species of *Caudipteryx*
state that the features lacked barbules, and another
analysis listed here but which I cannot remember the
citation for suggested *Archaeopteryx* had solid
raches (it may have been in the _Beginnings of Birds_
volume).

<I remember my geometry teacher saying something to
the effect that to prove something true, you need many
logical and mathamatical steps, but to disprove it,
all you need is a single equasion.>

  You need unequivocal data to substantiate any given
hypothesis, and similar for disproving the hypothesis;
hopefully, you can do both without ever leaving the
notepad. If not, you have support. Try disproving your
statement. Several others on the list are doing the
same.

<You've got all these elegant, logical and
mathematical steps, and I've got the equasion.>

  What is it?

<....Hey, life has gotten some pretty weird children.
Look at spirula and graphitites, I know that neither
is a vertibrate, but both evolved to look exactly like
another group.>

  The vertebrate skeleton imposes certain restrictions
to morphological variation, and in basic diversity,
invertebrates are much more plentiful (by the millions
and billions) and plastic than vertebrates.

=====
Jaime "James" A. Headden

  Dinosaurs are horrible, terrible creatures! Even the
  fluffy ones, the snuggle-up-at-night-with ones. You think
  they're fun and sweet, but watch out for that stray tail
  spike! Down, gaston, down, boy! No, not on top of Momma!

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