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re: mesosaurus

David Peters (davidrpeters@earthlink.net) wrote:

<I appreciate all of the refs and web grams that show Mesosaurus outside
of the diapsida, but what I really what to see is a good account of it. If
anyone has the ear of Sean Modesto or has his PhD thesis in a file
somewhere, I'd like to hear from you.>

Here is a good account for lineages basal to a Diapsida:

  Berman, D. S., R. R. Reisz, D. Scott, A. C. Henrici, S. S. Sumida, and
  Martens, 2000. Early Permian bipedal reptile. _Science_ 290:969-972.

  Carroll, R. L. 1988. _Vertebrate paleontology and evolution._ (W. H.
  Freeman and company, New York, 1988, 698pp.)

  deBraga, M. & R. R. Reisz. 1996. The Early Permian reptile
  *Acleistorhinus pteroticus* and its phylogenetic position. _Journal of
  Vertebrate Paleontology_ 16(3):384-395.

  Laurin, M., J. A. Gauthier, and S. B. Hedges. 1996-1997. Amniota -
  Mammals and reptiles. iNet: The Tree of Life:

  Laurin, M. and J. A. Gauthier. 1996-2000. Phylogeny and Classification
  Amniotes. iNet: The Tree of Life:

  Lee, M. S. Y. 1996. Correlated progression and the origin of turtles.
  _Nature_ 379:812-815.

  Lee, M. S. Y., 1993. The origin of the turtle body plan: Bridging a
  famous morphological gap. _Science_ 261:1716-1720.

  Modesto, S. P. 1999. Observations on the structure of the Early Permian
  reptile *Staurosternon tuditum* Cope. Paleontologica Africana 35:7-19.

  Modesto, S. P. 2000. *Eunotosaurus africanus* and the Gondwanan
  of anapsid reptiles. _Paleontologica Africana_ 36:15-20.

  Sumida, S. and S. P. Modesto. 2001. A phylogenetic perspective on
  locomotory strategies in early amniotes. _American Zoologist_

  Plus previously cited references, those especially with phylogenies.

  Note that in some of these, Diapsida equals a clade within Eureptilia,
essentially Araeoscelidae + Neodiapsida, Eureptilia being all members of
the Sauropsida which AREN'T parareptiles (to which Mesosaurids have been
found at the base of). Also note that some gene trees find a different
position for turtles, and that the position of turtles is not settled, but
it would seem as if the fossils either go WITH turtles wherever they end
up, or stay where they are and show MASSIVE amounts of morphological
parallelism. Not as recently, some trees put *Claudiosaurus* and
*Mesosaurus* in a grade at the base of Sauropsida, outside the
Parareptilia/Diapsida split (some use Diapsida instead of Eureptilia, some
use Diapsida FOR Parareptilia+"Diapsida" and some use Anapsida for

  Also, what has or has not been falsified remains up to debate when and
until anyone can test YOUR findings. Until then, statements about the
"real" position are anecdotal.


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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