Re: Crocs and such(io)

["Mickey Mortimer" <Mickey_Mortimer111@msn.com>]

Peter Markmann wrote-


> My thanks to all who've chimed in on the 'why crocs aren't dinosaurs'
> question. Cladistics notwithstanding, I still have trouble with the
> notion that budgerigars are dinosaurs whilst alligators are not. It's
> interesting that tooth and jaw characteristics hold less weight (no
> pun) than leg posture when determining the criteria for dinosauria.

You have to remember it has to do with relationships, not necessarily
anatomy.  In this case, anatomy is the main criterion for deciding
relationships, but a LOT of features are taken into account.  No one
character is good enough to prove that a taxon is a dinosaur, you have to
use to total distribution of every character you can.  Which is why
cladistics is so complex.

> I wonder: when did crocs and dinosauria diverge?

In the Triassic.  Taxa more closely related to crocodilians are called
crurotarsans, and include ornithosuchids, phytosaurs, aetosaurs,
rauisuchids, poposaurids, sphenosuchians and other crocodiliformes.  Taxa
more closely related to dinosaurs are called avemetatarsalians, and include
Scleromochlus, Lagerpeton, Lagosuchus, Marasuchus, Pseudolagosuchus,
Lewisuchus, Silesaurus and maybe pterosaurs.

Mickey Mortimer