Edmontosaurus [was: Re: The Holy of Holies... Dinosauria II]

["Jonathan R. Wagner" <jonathan.r.wagner@mail.utexas.edu>]

In response to HPs Marisa and Bigelow:

The taxonomy of the Edmontosaurus clade is badly in need of review. I was, 
at one time, slated to do this as part of my dissertation. Many of the 
supposed differences in the species of Edmontosaurus appear to be due to 
preservational differences (differential crushing, including the 
ever-popular "Edmontosaurus squish"). Also, many Ed specimens are partly or 
wholly reconstructed, which can exaggerate percieved differences tremendously.

Based on the specimens I have seen, and the literature, I see no convincing 
evidence that E. edmontoni is distinct from E. regalis, nor that E. 
saskatchewanensis is distinct from E. annectens. This is conveniently in 
accord with stratigraphy as well. However, because I have not seen the 
types firsthand, I do not feel I can make a definitive statement at this time.

I haven't seen any evidence of sexual dimorphism in Edmontosaurus either, 
but I really wouldn't be surprised. Certain recent papers on the subject 
aside, dimorphism appears to be ancestral for hadrosaurs... whether or not 
it is lost in the "saurolophines" (Saurolophus and Edmontosaurus) is an 
open question. There is a reasonable amount of E. annectens out there, so a 
study of this *is* possible.

Wagner


Alessandro Marisa wrote:
> And what about Edmontosaurus saskatchewanensis? It's more closely related to
> E. regalis or to E. annectens+"A". copei? My first suggestion is to E.
> regalis, but I don't have nothing about E. saskatchewanensis a part for the
> skull present in "The Dinosauria" and in Horner 1992 monograph on
> Prosaurolophus.

Phil Bigelow  wrote:
> Is it possible that sexual dimorphism could be responsible for some of
> the diagnostic confusion between the 3 species (4, if you include
> _saskatchewanensis_)?