Stegosaurus ungulatus and S. armatus

[Amado Narvaez <anarvaez@umd5.umd.edu>]

I was admiring the Battat/Museum of Science in Boston Stegosaurus 
ungulatus and decided to look up information about the creature in my 
collection of reference materials. Lessem and Glut's _Dinosaur 
Encyclopedia_ suggests that 1) the species S. ungulatus may actually be 
the same as S. armatus, and 2) "there may have been four pairs of tail 
spikes." I was surprised that there was any uncertainty at all about the 
number of tail spikes. Most restorations confidently depict four pairs of 
tail spikes. Can anyone explain for me why the uncertainty exists at all? 
(I'm anticipating that the kids at my school are going to question the 
accuracy of the 8 spikes of the Battat stego since for most of them there is 
one and only one Stegosaurus -- S. stenops, which has only 4 spikes.)

(BTW, when I first went around looking for the Battat/Museum of Science 
dinosaurs, the only thing I found was a set of cheap Battat models that 
were rather inaccurate. Don't get confused between the ones that are simply 
"Battat" and the ones that are "Battat/Museum of Science" figures. The 
Museum of Science ones are the same scale as the Carnegie dinosaur 
figures but more accurately and more dynamically posed.)

----- Amado Narvaez
      anarvaez@umd5.umd.edu