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Re: Dinosaurs Unearthed in Niger



>> Paul Sereno's article includes some preliminary work done on a
>> 'camarasaur'...
>> > The herbivorous dinosaur has not been named but is unusual because it
>> > represents a form -- typified by broad teeth -- that was thought to have
>> > become extinct more than 20 million years earlier. It was about 55 feet
>>long.
>> > Its thigh bone is six feet long.
>>
>> Question...
>> It seems that this sauropod material was discovered prior to Sereno's
>> field work, I think it was by a French paleontologist named Lapparent or
>> Lavocat in late 1950's, but the site was abandoned.  Was this material
>> considered to be the dinosaur Rebbachisaurus sp.?

Some of the fossils called "Rebbachisaurus" may indeed be referrable to
this new taxon.  The problem is that all named species of Rebbachisaurus
are based on very fragmentary materials, not all of which might belong to
the same family of sauropod.  Sereno et al. want to hold off until they've
got a better idea of what (if anything) is Rebbachisaurus, and what is not.

Incidentally, some of us are not convinced that their new sauropod is a
camarasaurid.  Broad teeth may be a primitive feature for sauropods, and
the denticles on the teeth of the new species are very primitive for a
Cretaceous form.  The neural spines are undivided (bifurcating neural
spines have often been considered a characteristic feature of true
camarasaurids).

One problem I had with this paper was their statement that "broad-toothed"
sauropods had gone extinct at the end of the Jurassic.  Brachiosaurids
(including their broad teeth) are found in many Early Cretaceous deposits,
and a possible camarasaurid is known from the Wealden (a European deposit
from the same age as the new Niger forms).

                                
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.