Re: intro into Ultra

[Tom Holtz <tholtz@geochange.er.usgs.gov>]

>Hi, I'm new to this list and I'm a second grade teacher.  You'll be amazed at
>what the little guys know and want to know about dinos.  They're fasinated by
>the big boys as well as the big eaters.  Is there any updates on finds
>concerning Ultrasaurus and/or Supersaurus?  Where can I get some good but
>simple info.
>Thanks in advance.
>Mr. Starkosaurus

You could try Glut & Lessem's (or was it Lessem & Glut?) Dinosaur Society
Dinosaur Encyclopaedia, but even that doesn't have the latest information:

Ultrasauros (-os and not -us do to some taxonomic mix-ups in the 1980s) is
a giant brachiosaurid, and may just be an extra-large individual of
Brachiosaurus altithorax.  Estimates put it at the 45-50 tonne range.

Supersaurus is a large diplodocid, and might be an extra-large Diplodocus,
Barosaurus, or something else.  Its been estimated at about 50-55 tonnes.

Seismosaurus appears to be a very long diplodocid, which might be distinct
from Supersaurus.  It is probably also in the 50-55 tonne range.

All of the above are from the Morrison Formation, an Upper Jurassic deposit
in the western U.S.

However, none of these are as big as the REALLY big sauropods:

Argentinosaurus, a gigantic titanosaurian from the mid-Cretaceous of
Argentina, is estimated at 80-100 tonnes, or equivalent in mass to the
modern fin whale (second largest living creature).  Some other Argentine
titanosaurs (Argyrosaurus, Antarctosaurus, etc.) may reach equivalent
sizes.

And, there was a piece of a vertebra found in the Morrison Formation which
was given the name Amphicoelias fragillimus.  IF that piece was as big as
it was illustrated (the actual fossil has since been lost) and IF
Amphicoelias had the same proportions as smaller diplodocids, than it may
have been over 100 tonnes.

In any case, despite a lot of press otherwise, Supersaurus and Ultrasauros
are not the largest sauropods.

Hopes this helps.

                                
Thomas R. Holtz, Jr.                                   
tholtz@geochange.er.usgs.gov
Vertebrate Paleontologist in Exile                  Phone:      703-648-5280
U.S. Geological Survey                                FAX:      703-648-5420
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092
U.S.A.