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Re: Stegosaurus species



In a message dated 10/15/99 7:20:55 PM EST, sarima@ix.netcom.com writes:

<< My Web site currently lists _Stegosaurus_ _ungulatus_ as a junior synonym
 of _Stegosaurus_ _armatus_.  It has recently been suggested to me that they
 have different numbers of tail spikes (four and two respectively), thus
 precluding them from being in the same species.
 
<< Is this argument valid?  Do they really have different numbers of tail
 spikes, or is this only an *apparent* difference to the _S. armatus_
 skeleton being incomplete?  Or is something else going on here?  Certainly
 Galton in Weishampel's _The Dinosauria_ makes them synonyms.  It seems
 unlikely to me that he would make such an elementary error. >>

As originally mounted, Stegosaurus ungulatus was shown with eight tail spikes 
(in four pairs), but the actual number remains conjectural. We now know that 
?Stegosaurus stenops had four tail spikes, but quarry maps in Gilmore's 
monograph on the Stegosauria show at least one specimen in situ with five or 
six spikes. The "genoholotype" specimen of Stegosaurus armatus is encased in 
hard matrix and has never been prepared, but enough of the skeleton is 
exposed to show considerable similarity to Stegosaurus ungulatus. On the 
other hand, it also shows some differences (taller neural spines and 
relatively larger plates, for example) from the Stegosaurus ungulatus type 
specimen, so it may be best not to refer S. ungulatus to S. armatus anymore. 
Peter Galton tells me he will be publishing more on stegosaurs in the near 
future.