RE: Stegosaur volume of Swiss Journal of Geosciences

[Tim Williams <tijawi@yahoo.com>]

Michael Mortimer <mickey_mortimer111@msn.com> wrote:


> Looks quite interesting.  However, in his abstract Galton
> writes "Stegosaurus armatus Marsh 1877, based on a partial
> tail and a very large dermal plate from the Morrison
> Formation (Late Jurassic) of Morrison, Wyoming, USA, is a
> nomen dubium." and "The International Commission on
> Zoological Nomenclature (ICZN) will be petitioned to
> designate S. stenops Marsh 1887 as the new type species of
> Stegosaurus Marsh 1877 in order to conserve Stegosauria
> Marsh 1877 and Stegosauridae Marsh 1880 (also
> Stegosauroidea, Stegosaurinae)."  This seems like the same
> flawed rationale used when Titanosauridae was killed by
> Wilson and Upchurch (2003) because Titanosaurus was declared
> a nomen dubium.  

I think the rationale is appropriate.  If _Titanosaurus_ is a nomen dubium, 
than it is perhaps best to exclude 

> Yet the ICZN says nothing about families
> needing to be based on diagnostic taxa, it just says a taxon
> should be "well known" if it has a family-level group named
> after it. 

This is a distinction without a difference, surely.  If a taxon is a nomen 
dubium, than it can't be "well known".  

In the parlance of phylogenetic nomenclature, a nomen dubium is not a valid 
operational taxonomic unit (OTU), and so effectively does not exist.  So from a 
phylogenetic taxonomic perspective, having families named after suspect taxa 
can lead to instability.  I recall having this discussion using _Ceratops 
montanus_ as my poster child for why it was a BAD idea to maintain a family 
called Ceratopsidae when the nominative taxon (_C. montanus_) was too poorly 
known to be confident if it actually belonged in Ceratopsidae.

Designating _stenops_ as the new type species for _Stegosaurus_ seems an 
entirely sensible suggestion, IMHO.


Cheers

Tim