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Ken Kinman wrote-
> Are you perhaps suggesting that Malawisaurus and Nemegtosaurus might
> rather distantly related. I can't remember who proposed it, but some have
> thought that Nemegtosaurids are Diplodocimorphs rather than Macronarians.
> Or did that turn out to be based on convergences?
It would be Nowinski (1971) who first suggested Nemegtosaurus was a
diplodocoid (though the taxon was not in use at the time, he described it as
a dicraeosaurid). Only in the early nineties was a titanosaurian
relationship suggested. Upchurch (1994, 1998, 2000, etc.) has been
defending the diplodocoid side, but the discovery of Rapetosaurus seems to
have settled the matter for the titanosaurian camp. So, I do believe
titanosaurs had widely varying cranial morphologies. The more basal types
like Malawisaurus were camarasaur-like, while at least a clade containing
Nemegtosaurus, Quaesitosaurus and Rapetosaurus were diplodocoid-like.
Phuwiangosaurus is said to have a nemegtosaurid-like skull, but is currently
placed at the base of the Titanosauria. Braincases are known for
Antarctosaurus, "Apatosaurus" minimus, Lirainosaurus, Saltasaurus and
Titanosaurus, but few titanosaur snout remains have been found.
Campylodoniscus is a maxilla from the Bajo Barreal Formation of Argentina
that resembles Malawisaurus, so is probably titanosaurian. A similar
maxilla was found in India and has been referred to Titanosaurus.