Re: Ankylosauria and Scelidosaurus

[Jay <sappororaptor@yahoo.com>]

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

--- Tim Williams <twilliams_alpha@hotmail.com> wrote:

> Jay <sappororaptor@yahoo.com> wrote:
> 
> >Another possibility would be Ankylosauria be *restricted to Nodosauridae + 
> >Ankylosaurid*.
> 
> One potential downside to the above definition is that we might have a 
> situation in which there are traditional ankylosaurs that fall outside the 
> clade bounded by _Nodosaurus_ and _Ankylosaurus_.  For example, if future 
> analyses uphold the validity of Polacanthidae, then polacanthids would not 
> be ankylosaurs under the "Nodosauridae+Ankylosauridae" definition.
> 
> >In this case, it doesn't really matter if Nodosauridae turn out to be 
> >paraphletic to Ankylosauridae or
> >not.
> 
> Given that Nodosauridae (stem-based) is defined by Sereno to include 
> _Nodosaurus_ and _Panoplosaurus_ but not _Ankylosaurus_, a paraphyletic 
> Nodosauridae would probably be invalid.
> 
> >Bottomline: Wheather Scelidosaurus becomes is closer to Ankylosauria or 
> >outside Eurypoda isn't
> >going to change the clade names, which seem pretty stable in my opinion 
> >(the definitions of).
> 
> Agreed.
> 
> Cheers
> 
> Tim
> 
> 
> 


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