Conservatism of dinosaur brain cases

[jrw6f@faraday.clas.virginia.edu]

The following point was delayed while Wagner brushed up on e-mail form
and ettiquette (but still not on his spelling) [and not his subject
line insertion.  Hope you like the one I picked! :-) -- MR]:

Diongeorge wrote (many moons ago...):

   >An inflated basisphenoid capsule and other advanced theropod
   >features of the skull of _Erlikosaurus_ are almost certainly not
   >homologies. Any anatomist can find hundreds of character loci within
   >the intricate anatomy of a typical [e-mail error here]
   >dinosaur skull, so it is not surprising that some of these, now and
   >then, present similar structures in similar-looking but not closely
   >related species. Dinosaur skulls are outrageously variable and any
   >supposed cranial synapomorphies uniting taxa above the generic level
   >require more salt grains than usual.

   Here I cite Currie's article in the May 17th issue of Science,
where he says:

    "[Dinosaur] [b]rain cases are conservative, which makes them
excellent tools for studying relationships because they are less
susceptible to rapid evolutionary changes that characterize skeletal
structures associated with feeding and locomotion."  (He omits
reproduction)

        Phillip J. Currie, _Out of Africa: Meat-Eating Dinosaurs That
        Challenge Tyrannosaurus Rex_, Science 272, 971-2 (1996)

          The parasphenoid is a part of the braincase of bullatosaurs,
and is considered a high weight novelty by most workers.  I think it
is very likely that, with enough detailed work, these will be shown to
be not only homologous, but synapomorphic.  In any case, I think
Currie's statement goes a long way toward refuting your premise.

Did I just volunteer to do something?
Dino: Danke, pozhalsta, gracias, merci, sheshe, werd! Anyone else got
any refs?
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! Jonathan R. Wagner                        !   "Camin-Sokal Pars-      !
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