Re: Sauropods

["Matthew Bonnan" <mbonnan@hotmail.com>]

Dino Rampage:

You have a lot of sauropod questions, so I will only answer one for right 
now.

You asked:
"4) What features are there to differentiate Eobrontosaurus yahnahpin from
Apatosaurus?"

I have looked at the "Eobrontosaurus" material during my dissertation.  From 
what I could tell, it is an apatosaur and comparing the shape of the 
forelimb, manus, and pes especially, I don't get the sense that this is very 
much different, if at all, from Apatosaurus excelsus.  This is my opinion 
based on what other Apatosaurus material I've seen, and there are probably 
those who would disagree with me.  However, I did not notice any features, 
at least as far as the limbs were concerned, that warranted any erection of 
a new genus name, and perhaps not even a new species name.  But again, this 
is my opinion based on what I've seen -- it just didn't look all that 
different to me, and with the shape analysis I've used to look at 
differences in sauropod bones, Apatosaurus yahnahpin did not differ 
significantly from any of the other apatosaurs in appendicular bone shape.  
It is a very well-preserved specimen and in excellent shape -- if you 
haven't seen it in person and you're interested you should.  Very nice 
preservation -- probably one of the best preserved apatosaurs in the world, 
although certainly not the most complete.

"And is there sufficient evidence to warrant placing Apatosaurus
excelsus in Brontosaurus?"

Whether we like it or not (and many folks don't), Brontosaurus was sunk as a 
name when it was discovered that Apatosaurus was the same animal as 
Brontosaurus but was named earlier on scrappier material.  The strict codes 
of zoological nomenclature tell us that, since Apatosaurus was the first 
name given to the material, Brontosaurus is now invalid or a junior synonym. 
 Some people argue that because Marsh named both specimens there isn't 
really a problem, and that Brontosaurus should be resurrected as a valid 
genus name.  I think this would cause more confusion than help right now, 
because so many articles have used Apatosaurus -- we'd have to go back 
through a hundred years of literature or more and sort out what who meant by 
what and what specimens they were referring to.  What a nightmare!  Anyway, 
there are others on this list far more knowledgeable than I when it comes to 
zoological codes, taxonomy, and systematics, so they may have a better 
perspective on this than me.  However, I really don't see that Brontosaurus 
and Apatosaurus excelsus are all that different from each other (in fact, I 
can't think of a single significant morphological difference) that would 
warrant a name change.


Okay, one last tidbit:
"Personally, I find it
hard to believe that the diplodocids, dicraeosaurs, rebbachisaurids,
brachiosaurs, camarasaurs and a whole host of other sauropod groups could
have survived with the titanosaurs."

This is where the confusion and interest comes in with titanosaurs.  We just 
don't know.  Our record of titanosaurs is still relatively poor to have a 
good idea of what is going on with them as a group.  Maybe diplodocoids, 
brachiosaurs, and camarsaurs DID survive in good numbers into the Cretaceous 
and they ARE what we call titanosaurs.  Titanosaurs seem to be a hodge-podge 
of neosauropod characters and perhaps this is because they actually 
represent the two major neosauropods groups in their "new" Cretaceous forms. 
 Or, maybe they were a new group of neosauropods, etc.  We just don't know 
right now.

Hope some of this helps or stimulates other conversation about sauropods. =)

Matt

Matthew F. Bonnan, Ph.D.
Department of Biological Sciences
Western Illinois University
Macomb, IL 61455
(309) 298-2155
mbonnan@hotmail.com
MF-Bonnan@wiu.edu

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