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Fwd: RE: Sauroposeidon

I would like to add my two cents to the brachiosaur/titanosaur discussion - as 
some of those 
attending SVP know, DMNH has a couple of new EK sauropods which which Ken 
Carpenter and I are 
describing. (This topic is directly addressed in the soon to be published paper)

On 11/03/99 16:43:04 Tim White wrote:

>According to Salgado, the "Pleurocoelus" material from the Early Cretaceous 
>of Texas is bona fide titanosaurid, judging from the procoelous anterior 
>tail vertebrae.  The _Astrodon_/_Pleurocoelus_
>type material from Dr Holtz's stomping ground of Maryland, on the other 
>hand, is probably basal titanosaur.  Its tail vertebrae are different to the 
>Texas sauropod.

Yes, the tail vertebrae are different in these two "Pleurocoelus" specimens, 
with the Maryland 
specimens having amphiplatyan caudal verts.  However, to call the Texas caudals 
"Procoelus" may 
be stretching that definition too far.  The anterior face is concave, but the 
posterior face is 
flat, without the distal ball which has traditionally been used to diagnose 
titanosaurs.  Also, 
several new sauropods have recently been excavated having concave anterior 
faces and flat 
posterior faces. The whole definition of "procoelus" needs to be refined over 
the next few 
years, as finer grades of procoely are discovered.  

Salgado classified the Texas "Pleurocoelus" as a basal titanosaur based also on 
the transverse 
expansion of the distal end of the tibia, which is a character shared with 
Malawisaurus and 
Saltasaurus, both established titanosaurs.

>The humerus/femur ratio shared by the two _Brachiosaurus_ species has also 
>been questioned.  This was news to me when I read it, but the humerus of _B. 
>brancai_ is apparently incomplete.  The two species may not be comparable in 
>this respect.

Riggs' description of B. altithorax states that a portion of the femural head 
was already eroded 
when the specimen was recovered. So, instead of the humerus / femur ratio being 
>1, it may =1 or 
be just a little shorter.  In a recent discussion of this subject with Salgado, 
he stated that 
he knew of no titanosaur having a humerus/femur ratio that was close to 1/1. 
So,IMHO, any 
specimen with a very high H/F ratio, while lacking the transversely expanded 
tibia and distal 
ball on caudal verts should still be included in the family Brachiosauridae.  
That is, until a 
better family definition is hashed out, utilizing all of the new EK brachiosaur 
material coming 
to light in the Western U.S.

Virginia Tidwell
Denver Museum of Natural History
2001 Colorado Blvd.
Denver, CO  80205

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