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Re: SYNTARSUS/MEGAPNOSAURUS



David Marjanovic (david.marjanovic@gmx.at) wrote:

<While it is wisest, there is a simpler choice -- to call it
*Coelophysis*.   The only conspicuous difference from *C. bauri* is that
it lived later, after all.>

  No, there are more. Including ankle morphology, and head morphology.
Also, ther do not seem to be as much gross variation in head size between
the two "morphs". Problematically, while Paul (1988, 1994) supported
including *S. rhodesiensis* into *Coelophysis*, you'd still have two
species. At any point, the trees are identical and you're just using ranks
to differentiate use of names. This is ridiculous, in some ways; the
species are distinct, so at which point the names can reflect this, and
how far, is a matter of taste to the researcher. The Rhodesian species and
the Kayenta species have features not found in the Petrified Forest
species (ankle morphology is most significant); the Petrified Forest
species and Rhodesian species have features not found in the Kayenta
species (no crests, generalized snout morphology, more teeth). Wherever
you draw the line, as demonstrated by differences in _The Dinosauria_ and
_Predatory Dinosaurs of the World_ as an issue of rank-based phylogeny or
species only OTU's where *Coelophysis* ceases to have much meaning unless
_it's_ the species. Or, one could say the same thing as between some
dromaeosaurid or "dromaeosaur" taxa (like Paul's suggested synonymy of
"sinornithosaurs" and "microraptors" ... classic in his works as a
"lumper" method, even though even his phylogeny suggests different and so
do the other ones involving relevant taxa). Or hadrosaur species. Or some
ankylosaurids like the problem with Chinese-Mongolian *Saichania*-like
taxa, as well as the apparent identical nature of *Nodocephalosaurus* from
the Maastrichtian of North America. They are all virtually identical. But
there are differences. These relate to other taxa where one can find
monophyletic clades if one includes enough _or_ excludes enough
characters, or polyphyletic series of taxa, with the same issue. Or one
can use the "feels good" method. Or the "Jefferson's Horse" analogy.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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