Re: diplodocid radiation

[Adam Yates <zooamy@zoo.latrobe.edu.au>]

On Sat, 23 Mar 1996 GSP1954@aol.com wrote:

> As for nemegtosaurs being diplodocids, I'm the Pope. Odd how no one has ever
> found any diplodocid postcrania in L Cretaceous Asia, especially when
> sauropod skulls are much rarer than skeletons. Also odd how no one has found
> camarasaur teeth there and then. All that is known from L Cret Asia are
> pencil teeth, nemegtosaur skulls, and opisthocoelicaudian skeletons! It does
> not take a rocket scientist to put these together into one sauropod type. 
> 
> GSPaul

I had always thought that the Nemegtosaurus skull looked a lot less like 
diplodicids than had been made out, so I was very pleased when Upchurch's 
parsimony analysis found them to be outside of the 
diplodicid-dicraeosaurid clade. One aspect of Nemegtosaurus puzzles me, 
the dorsal surface of the rostrum is always dotted in lateral views (and 
indeed photos seem to show that this area has broken away, yet the skull 
is restored in dorsal view confidently. It shows a single diplodicid 
like narial opening, however this should not be determinable if the 
dorsal surface of the rostrum is missing. Indeed it could have had a 
more primitive (Euhelopodid like) snout. Until a good Titanosaurid skull 
is found we can't be sure that the entirely cranial synapomorphies of 
Upchurch's Diplodicoidea aren't infact  apomorphies of the larger 
Titanosauroidea + Diplodicoidea clade. BTW is the Titanosauria the 
valid name for this larger clade?

Adam Yates