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RE: Stegosaur volume of Swiss Journal of Geosciences



--- On Sat, 18/9/10, Michael Mortimer <mickey_mortimer111@msn.com> wrote:

> 
> So really, S. armatus should get a neotype instead of S.
> stenops being made the new Stegosaurus type. If we were
> following the ICZN that is.

But how would you select a neotype, knowing that neotype is not actually 
material of S. stenops? Say one selects a neotype, and it is shown that is 
obviously not of S. stenops, but then how you know that material is not of 
another species (apart from S. stenops) or Hesperosaurus? To answer, obviously 
if it's from a new form.

For argument, let's assume the S. armatus type is undiagnostic within a certain 
clade of stegosaurian taxa. Thus any selected neotype needs to be of a form 
different (diagnosable) from the types of the other taxa already within that 
clade. Effectively, it would come from material of the next stegosaur 
species-taxon that would have been recognised (and named) had no neotype been 
searched for.

Galton indicated in his paper that in future a proposal would be submitted to 
the ICZN to fix a new genotype for Stegosaurus: S. stenopes. But, the next 
named species for which anatomically well known types and material exist is 
Stegosaurus ungulatus (based on significant cranial & postcranial material). 
Galton's rationale for choosing S. stenops over other replacement genotype 
candidates is as follows:
"As noted above, USNM 4934, the holotype of Stegosaurus stenops MARSH 1887, has 
all 12 autapomorphies listed by Maidment et al. (2008) for ââStegosaurusââ and 
ââS.ââ armatus and, in addition, it is the only holotype with characters 8 and 
12."

IMO, S. ungulatus is is based on adequate diagnostic material, and should be 
the first choice as a replacement genotype, not S. stenops.