Re: An even dumber question

[zone65@bigpond.com]

On Saturday, April 17, 2004, at 07:52  PM, T. Michael Keesey wrote:

> --- zone65@bigpond.com 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
> outside.
>
> Dinosaurs and their closest relatives, such as _Silesaurus_,
> _Pseudolagosuchus_, _Lagosuchus_, and _Marasuchus_, form the 
> _Dinosauromorpha_,
> a group characterized by, among other things, upright limbs.

Although, crocs do stand, walk and run with their limbs upright at 
times. And triceratops (at least) had a 'bent elbow' posture. Is the 
stance really enough to differentiate crocs from members of dinosauria? 
And aren't cladistics like statistics, in that they can be made to 
'prove' desired results?

Peter Markmann