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RE: Stegosaur volume of Swiss Journal of Geosciences

Jay <sappororaptor@yahoo.com> wrote:

> Okay, lets assume for now the material of S. armatus can be
> distinguished from Huayangosaurus, thus allowing stegosaurs
> to be placed in either Stegosauridae or not with S. armatus
> and H. taibaii being internal and external specifiers
> respectively:
> What if the issue is that the S. armatus material cannot be
> discriminated from that of Hesperosaurus, Dacentrurus,
> Loricatosaurus, Miragaia, Tuojiangosaurus, Wuerhosaurus etc?
> In this case, while the clade 'Stegosauridae' may continue
> to be upheld under your proposal, the clades Stegosaurinae,
> Dacentrurinae, and all the above genera would not if S.
> armatus was an internal specifier. Would all these taxa then
> be squeezed into 'Stegosaurus'? 

Jay hit the nail on the head here.  There is no point of having a genus if the 
type species is invalid.  As Jay points out, if _S. armatus_ is found to be not 
diagnosable at the genus level, but only at a higher taxonomic level (e.g, 
family or subfamily), then the entire concept of _Stegosaurus_ is destroyed.  
After all, a genus is only as good as its type species.  The entire point of a 
type species is to literally typify the genus.

This is why, when a type species is declared a nomen dubium, there are only two 
options: (1) retain the genus by designating of a new type species; (2) abandon 
the genus that is typified by the type species.  For _S. armatus_, option (1) 
seems the most appropriate, as was done with _Iguanodon_ before it.