Re: What exactly IS a dinosaur?

[David Marjanovic <david.marjanovic@gmx.at>]

> So, what's a dinosaur: an animal that's more closely related to 
> Saurischians
> and Ornithischians than it is to other animals.  In genealogical tree 
> terms,
> something descended from the most recent ancestor of S's and O's (and so
> descended from something that WASN'T an ancestor of any of the 
> non-dinosaurs
> listed.

More precisely: the most recent common ancestor of S's and O's, and all of 
its descendants. The way you wrote it, that MRCA would itself not be a 
dinosaur, so Dinosauria would be diphyletic...

> phylogenetic taxonomy

Phylogenetic nomenclature. There is no such thing as "phylogenetic 
taxonomy", even though you can find that expression in the titles of papers 
from the early 1990s (and more recent ones by Sereno).