RE: Precision, Ultra-, Super-, Seismo- and the like

[Mike Taylor <mike@indexdata.com>]

Botterweg, Rrp writes:
 > With regard to Ultrasaurus/Ultrasauros, wasn't the material
 > consisting of two species: (very large) Brachiosaurus and
 > Supersaurus.

Yes.  But the type specimen of _Ultrasauros_ was the brachiosaurid
anterior dorsal vertebra that Curtice et al. (1996) clearly
demontrated was actually a diplodocid posterior dorsal vertebra.  So
the names _Ultrasauros_ and _Supersaurus_ became synonymous, and
_Supersaurus_ won because although the two names were raised in the
same paper (Jensen 1985), it was the first of the two to be named.
(Shame, really, it's it's a rather lame name for such an awesome
beast.)

That left the referred scapulocoracoid, which is indeed brachiosaurid,
and which according to Curtice et al. (1996) cannot be separated from
_Brachiosaurus_.  Is it big?  Yes, though not as big as Jensen
implied.  It's certainly from a bigger animal than the _B. altithorax_
type specimen, which is still pretty much the only described specimen
of that species.  But it's not significantly larger than the largest
Tendaguru (_B. brancai_) scaps.

 > In that case, is the Brachiosaurus material just B. altithorax, or
 > another species, or is that impossible to say?

It's impossible to say, since no scapula of _B. altithorax_ has ever
been described -- the type specimen preserves a coracoid, but that's
not hugely diagnostic alone.  Curtice et al. just referred it to
_Brachiosaurus_ sp.

 > With regard to Supersaurus possibly being a synonym of Diplodocus:
 > if that is indeed the case then are Supersaurus and Seismosaurus
 > possibly also the same genus?

Unlikely, due to _Supersaurus_ almost certainly not being _Diplodocus_
-- see the earlier thread.

 > I ask this because I recently read ("Reappraisal of Seismosaurus, A
 > Late Jurassic Sauropod Dinosaur from New Mexico", annual conference
 > of the Geological Society of America, 2004) that Seismosaurus is so
 > similar to Diplodocus that it should be reassigned to that genus.

Patience :-)  Lucas et al.'s paper on this reappraisal should be out
very soon; then we can assess how strong their case for synonymisation
is.  Until then, it's all just talks, abstracts and chatter.

For what very little it's worth, the impression I get is that the more
of _Seismosaurus_ they excavate, the more it does look like a big
_Diplodocus_.  In particular, the initial description showed a very
oddly shaped ilium with a large posterodorsally directed process at
its distal end.  Now the other ilium is out of the ground, and it
doesn't have that process -- which, then, must be assumed to be a
pathology rather than a diagnostic difference.

But the jury is still out.

 _/|_    ___________________________________________________________________
/o ) \/  Mike Taylor    <mike@indexdata.com>    http://www.miketaylor.org.uk
)_v__/\  "_Apatosaurus_ sort of looks like a pro wrestler when most of
         the other sauropods tend to look like ballerinas" -- Matt Wedel.