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definition of dinosaur
I believe I read somewhere (I think it was here) that we should define
dinosaurs as all the descendants of the most recent common ancestor of
_Megalosaurus_ and _Iguanodon_.
I can provide that definition to my students (but I will have to follow
up with an explanation as to how they can recognize a dinosaur when they
see one). I predict that these questions will be asked about the
Why are those two genera singled out? Isn't it true that after all these
years we still do not have even one complete composite skeleton of
_Megalosaurus_? Why not choose _Allosaurus_, instead?
Do we really know when ornithischians branched off (separated?,
whatever--what would the correct cladistic term be?) from saurischians to
know that we're not leaving behind something like _Eoraptor_ or a
herrerasaurian? Let me rephrase that so no one here will jump on me for
misunderstanding _Eoraptor_ and herrerasaurs, which has nothing to do
with the point. Might we be leaving something behind that many people
would label as a dinosaur based upon its over-all anatomy (hips, sacrum,
limbs, feet, shoulder, neck, etc.)?
What is the closest thing we have discovered to that most recent common
ancestor of _Megalosaurus_ and _Iguanodon_?
As always, I (we) will appreciate any pointers.
Norman R. King tel: (812) 464-1794
Department of Geosciences fax: (812) 464-1960
University of Southern Indiana
8600 University Blvd.
Evansville, IN 47712 e-mail: firstname.lastname@example.org