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Mamenchisaurus? Aaaaaaaa...

On Thu, 1 May 1997, Sam j hogan wrote:

> I don't actually have the book, but the description sounds suspiciously
> like the mounting found in the atrium of the American Museum of Natural
> History in New York City.  Is the Mamenchisaurus  (identified as
> Barosurus in the museum's display) rearing up to defend itself and its

        I can grin now.  At first my heart stopped, but I realized it was 
simply my mind grinding to a halt.  Now I find it all quite amusing.  I 
can see how Mamenchisaurus and Barosaurus could become confused (heck, if 
we had the rest of the Supersaurus it'd be even easier to confuse, seeing 
how Supersaurus's neck is longer than that of Mamenchisaurus), loooong neck, 
"diplodocid" chevrons, sauropod body.  But rest assured the cast at the 
AMNH is *not* Mamenchisaurus (as Dr. Holtz already pointed out).  Rather 
it is, for the most part, a cast of AMNH 6341, the best preserved 
Barosaurus ever discovered.  A wonderful tale indeed, since Barnum Brown 
horse-traded such that the AMNH never even worked the Dinosaur National 
Monument from where the specimen heralds from.  Mamenchisaurus has, as 
best we can tell, more robust hind limbs (I know, I 
know, vagaries), but most importantly Mamenchisaurus has strongly (as 
opposed to gently) procoelous (read:  Big ball on back of vertebra) 
caudal vertebrae.  Plus the neural spines of Mamenchisaurus are far 
simpler in morphology, they are lower, supraprezygapophysial laminae 
isn't even well developed in caudals 8-12 (at least as far as I can 
determine after climbing all over the Los Angeles County Museum of 
Natural History Mamenchisaurus cast).  Note 
also the AMNH mount has the whiplash distal caudal vertebrae with fairly 
long distal chevrons and elongate caudal centra.  Contrast this with the 
LACM (or a good book figure) of Mamenchisaurus, which despite having 
"diplodocid" chevrons (the attribute that Marsh chose to name Diplodocus 
from:  "Double Beam Lizard") has rather antero-posteriorly shortened 
centra in the distal caudals.  Very Camarasaurus like.  Funny things indeed, 
and not at all what one would expect if only had first twenty 
caudal vertebrae had been preserved.  I wish another 
10 caudals had been preserved, it would have been most informative.  But 
that's why folks go into the field every summer...