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Re: An even dumber question
--- firstname.lastname@example.org wrote:
> What is it about crocodilians that makes them NOT dinosaurs? Ditto
> Komodo Dragons, other monitors, etc...
Originally, Dinosauria was recognized as a distinct group based on posture:
dinosaurs have erect limbs, with the feet placed directly under the body.
Crocodylians and varanids have the primitive sprawling posture, with the feet
placed further laterally.
More recently, _Dinosauria_ has been defined as a phylogenetic taxon, a clade.
One proposed definition would be: "The last common ancestor of _Iguanodon
bernissartensis_ and _Megalosaurus bucklandii_, plus all of that ancestor's
descendants." Crocodylians fall outside this clade, and varanids, along with
other lepidosaurs (lizards, snakes, mosasaurs, tuataras) fall much further
Dinosaurs and their closest relatives, such as _Silesaurus_,
_Pseudolagosuchus_, _Lagosuchus_, and _Marasuchus_, form the _Dinosauromorpha_,
a group characterized by, among other things, upright limbs.
=====> T. Michael Keesey <http://dino.lm.com/contact>
=====> The Dinosauricon <http://dinosauricon.com>
=====> Instant Messenger <Ric Blayze>
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