Re: Playing with Wilson and Sereno

[tidwell@ix.netcom.com]

What a joy to hear from another sauropod lover!  Yes, Wilson and Serenos' 
monograph impressed me as being a tremendous piece of work. And the absence 
of Mammenchisaurus was most frustrating.
Your comments on Haplocanthosaurus were quite interesting, as I have spent 
considerable time studying the three main specimens of Haplocanthosaurus.
They came from an area 2 hours from my home in Denver, Colorado.  Here at 
the Denver Museum we have recently recovered an additional partial skeleton 
from the same area.
  Unfortunatly, my grasp of cladistic analysis is poor. I can check whether 
specific characters do, indeed, apply to specific skeletons, but the 
further analysis goes way beyond me.  But your placement of 
Haplocanthosaurus as a basal Diplodocid surprised me.  Several skeletal 
characteristics seem to me to point in other directions:

The anterior caudal vertebrae do not have pleurocoels,
The mid and posterior caudal vertebrae do not seem to be elongated,
The cervical and dorsal vertebrae show no tendency towards bifurcation,
The skull of Morosaurus agilis resembles a Camarasaur, and is usually 
attributed to Haplocanthosaurus priscus.

What also puzzles me about this idea is that the holotype specimen for 
Diplodocus longus, which Jack McIntosh considers to be primitive for 
Diplodocus, was found in the same quarry, close by the holotypes for  
Haplocanthosaurus (priscus and utterbacki).  Finding a basal diplodocid 
next to a fully developed Diplodocus seems rather odd to me.

Just some thoughts off the top of my head...

Virginia Tidwell