RE: Sauroposeidon

["Timothy Williams" <twilliams_alpha@hotmail.com>]

Tom Holtz wrote:

> It is most assuredly not too recent for a brachiosaur, as at least SOME of
> the _Astrodon_/_Pleurocoelus_ material (contemporaneous with
> "Sauroposeidon") seems to be brachiosaurid.  Furthermore, there is now
> evidence of titanosaurs in North America by the mid-Cretaceous.

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.

> Of course, there is the whole question now of what other than 
> _Brachiosaurus
> altithorax_ and _B. (sometimes _Giraffatitan_) brancai_ IS a brachiosaurid.
> It may be that "Brachiosauridae" in the old more inclusive sense includes a
> paraphyletic grade of titanosaur outgroups.

As somebody pointed out recently (and for the life of me, I can't remember 
who), there's no apomorphic characters that link the Tanzanian/Tendaguru 
_Brachiosaurus_ (_B. brancai_) with the type species (_B. altithorax_) from 
the Morrison.  All the characters that link the two species, and have been 
used to diagnose the genus _Brachiosaurus_, are primitive titanosaur traits. 
 (This also applies to the family Brachiosauridae in the old more inclusive 
sense.)

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.

Remember, _Brachiosaurus altithorax_ is one of the more poorly known 
sauropods from the Morrison.  I agree with George in separating the 
Tendaguru species into a separate genus, _Giraffatitan_.


Tim

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