RE: new Western Interior dinosaurs: a brief breakdown

[Tim Williams <twilliams_alpha@hotmail.com>]

Thomas R. Holtz, Jr. wrote:

> > What is that? Google doesn't find "Hadrosauromorpha" or 
> "hadrosauromorph".
> >
> No taxonomic history of that name (only used in vernacular form) given. 
> Described as a non-
> hadrosaurid iguanodontian.

That would make it a hadrosauroid, I guess.  Interestingly, Hadrosauriformes 
is actually defined to include _Iguanodon_, whereas Hadrosauroidea is 
defined to exclude _Iguanodon_.

(from another message)...

> They "readily distinguish" _Dracorex_ from _Stygimoloch_ by the presence of 
> 4 short spikes in its spike cluster, rather than 3 hypetrophied ones (as in 
> the latter).
[snip]
> In other words, it differs from _Dracorex_ is nearly
> the same fashion that _Pachycephalosaurus_ differs from _Stygimoloch_. 
> Hmmmm... Altenative hypotheses as to taxonomic and ontogenetic status do 
> seem to raise themselves here, don't they?

I'm sure Tom already knows this, but Gangloff et al. (2005) noted that the 
arrangement and cluster of nodes varies quite a bit in _Pachycephalosaurus_. 
 This suggests that the details of nodes/spikes are prone to individual 
variation.  This was one reason why Gangloff &c actually held off naming the 
specimen that was subsequently named _Alaskacephale_.

> Sullivan, and Bakker et al., both question the value of cladistic analyses 
> on pachycephalosaurs at present.

Yeah, but does it hurt to try doing a cladistic analysis...?  :-)

> Authors also suggest that as the "principal character" of Marginocephalia 
> ("overhang of the occiput") is non-homologous between pachycephalosaurs and 
> ceratopsians in their interpretation, that Marginocephalia is not a natural 
> group. [snip]

I wonder what _Yinlong_ would say about that?

Cheers

Tim