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Re: Taxonomic Status
Ivan Kwan (firstname.lastname@example.org) wrote:
<Just what is Antarctosaurus? Is it a titanosaur, or is it (as i read
somewhere else) a
It's both. Or rather, the holotype of the type species, *A. wichmannianus*
von Huene, 1927, from
the Allen Fm. near Roca (same region and strata as *Quilmesaurus*), appears to
diplodocimorph, and possibly allied with *Nigersaurus*. The skull is especially
similar to several
diplodocimorphs, but is not as "rotated" so that the braincase faces ventrally
at the rear. The
mandible is especially diagnostic. A second species, *A. septentrionalis* von
Huene, 1932, was
removed as a titanosaurid called *Jainosaurus,* named for Sohan Jain, and was
titanosaur, and similar to both *Argyrosaurus* and *Titanosaurus.* A third
species, *A. giganteus*
von Huene, 1929, is also a titanosaur, from the Neuquén Fm.. Obviously, *A.
giganteus* is not
*Antarctosaurus.* Other titanosaur material referred to *Antarctosaurus* looks
material (see Curry-Rogers & Forster, 2001).
<By the way, did Titanosaur heads vary that much? I know that sauropod skulls
rare, but I have seen many restorations of them with squarish, camarasaur-like
heads, while the
recent finds of Rapetosaurus and Nemegtosaurus seem to show otherwise. What is
folks? Did some titanosaur families have square heads while others had slender
skulls? Or did all
of them convergently evolve a nice diplodocid-like head?>
Titanosaur heads did indeed vary, but the simple answer, I think, is not
transformation from a
boxy skull to an elongated skull, as supported by analyses with *Malawisaurus*,
plesiomorphic condition is that of a brachiosaur-type skull, which persists
Titanosauroidea and Titanosauridae, with some titanosauroids (nemegtosaurs)
having a more
diplodocoid-style skull, but the basal forms having a much more square skull
from the lateral.
Jaime A. Headden
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