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Re: Quaesitosaurus and Nemegtosaurus



At 05:48 PM 12/9/96 -0500, Tim Williams wrote (quoting George Olshevsky):

>> the postcranial skeleton of _O._ has many features found among
>> camarasaurids, whereas the skulls of _N._ and _Q._ seemed to be
>> diplodocoid. A recent reconstruction of the skull of _N._, however,
>> suggests close affinities with brachiosaurids, therefore also
>> camarasaurids, whereas Upchurch's cladistic study places _N._ and
>> _Q._ in their own family, Nemegtosauridae, as a basal sister group
>> to diplodocids.
>
>It's worth noting that Upchurch's cladistic analysis regarded 
>_Opisthocoelicaudia_ not as camarasaur or even a diplodocoid, but as 
>a titanosaur.  The postcranial skeleton of _O._ has a close OVERALL 
>similarity to camarasaurids, but when it comes down to the nitty-
>gritty, there's not too many synapomorphies linking the two together.
>
>More importantly, I heard a report somewhere that diplodocid-like 
>postcranial material was unearthed in the Nemegt Basin.  So, I'm 
>prepared to leave _N._ disembodied for the time being (and _O._ 
>without a head).

As George notes above, a recent study (by Calvo) shows that the skulls of
_Nemegtosaurus_ and _Quaesitosaurus_ are much less like diplodcoids than
reconstructed, and are actually very similar to _Brachiosaurus_!  I, too,
have heard tails..., er, tales of a Nemegt diplodocoid postcranial skeleton,
but have not had them confirmed.

Contra my previous thoughts on the subject (i.e., that "nemegtosaurids" were
diplodocoids), I find the evidence for _Nemegtosaurus_ and _Quaesitosaurus_
within a titanosauroid-brachiosaurid clade very compelling, and the
possibility that _Nemegtosaurus_ was the head of _Opisthocoelicaudia_ very
likely.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661

"To trace that life in its manifold changes through past ages to the present
is a ... difficult task, but one from which modern science does not shrink.
In this wide field, every earnest effort will meet with some degree of
success; every year will add new and important facts; and every generation
will bring to light some law, in accordance with which ancient life has been
changed into life as we see it around us to-day."
        --O.C. Marsh, Vice Presidential Address, AAAS, August 30, 1877