Nemegt dino update

[KELL00BELL@aol.com]

    There has been some confusion about the age of Alioramus.  Kurzanov 
considered it a Maastrichtian or Nemegtian tyrannosaur, but Paul wrote it was 
of Early-Late Cretaceous age.  The latter view was presumably based on 
apparently primitive stage of evolution.  However it now appears wrong.  The 
Nogoon Tsav locality, which yielded Alioramus, is definitely of Nemegtian 
age, based on turtles, ostracods, etc.  Moreover, the broad nuchal crest and 
downturned occiput of Alioramus suggust it is most closely related to late, 
advanced tyrannosaurs such as   T. bataar and T. rex.  Although Alioramus is 
relatively small, and its snout long and low, these are probably juvenile 
features.  The Maastrichtian age is consistent with a large, derived 
tyrannosaur, and Alioramus may be a species of Tyrannosaurus.  Its absence 
from all Nemegtian localities except Nogoon Tsav, however, suggests it 
originated in some other Asian environment.
    Some work on Nemegt dinosaurs came too late for inclusion in the new 
Cambridge University Press volume.  Sauropod caudals unearthed at the type 
locality in 2000 are shallowly procoelous.  It is now clear that two sauropod 
taxa are present in the Nemegt; obviously the new material is not 
Opisthocoelicaudia.  Strangely, the tail was the only sauropod material seen 
by the 2000 expedition, despite an earlier report by the AMNH of "lots" of 
uncollected sauropods.  I had assumed that these were at the type locality,  
since the AMNH expedition was at adjacent Khulsan.
    --Tim