Re: Ankylosauria and Scelidosaurus

[Nick Gardner <nick.gardner@gmail.com>]

On 4/24/06, Jay  wrote:
> Yeah Tim. I agree with you here.
> I didn't really mean to go into ankylosaurian phylogeny too much before, and 
> should have just
> stuck to the definitions asked for.
>
> I personally guess that both Nodosauridae and Polacanthidae are paraphyletic 
> with respect to
> Ankylosauridae.
> I personally favor the definition currently in use for Ankylosauria rather 
> than the second
> possibility i put forward, which you commented on.
> Allying other 'nodosaurids' to Nodosaurus as an internal specifier is a bit 
> risky considering how
> little is known of the animal relative to Panoplosaurus, Edmontonia, 
> Gargolylesaurus &
> Ankylosauridae. What if Nodosaurus is a very basal ankylosaurian? That would 
> result in
> Nodosauridae and Ankylosauria being the same thing, with the current 
> definition. Not that i think
> it's or know it's basal, but just putting it forward.
> To clarify, i thought the current definitions of the higher Thyreophoran 
> clades were pretty
> stable. I'm not so sure about the stability of the definitions
>

With all due respect to the ornithischian workers onlist (I'm sure
there must be some out there, somewhere!), perhaps it's time to
declare a moratorium on defining and naming clades within the group
until their relationships are better understood. Taking into
consideration published analyses like Butler's, and various
unpublished analyses by myself and others, I really believe that
overall our current understanding of ornithischian relationships is
flawed, and that attempting to define the clades given the current
circumstances may be a disaster waiting to happen.

My two cents,

Nick Gardner