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Re: Bahariasaurus & other questions

"Dino Rampage" wrote-

1) What is Bahariasaurus ingens? Is it a carnosaur closely related to the carcharodontosaurines (as was traditionally assumed) a basal tetanuran with unknown affinities, or is it possibly a basal coelurosaur similar to Deltadromeus?

PAUL 1988 placed it as the closest allosaurid to the Tyrannosauridae, but I think that much of that was based on material now referred to Deltadromeus. SERENO et al 1996 do not consider a placement for this taxon but refer the material to D. Mikko Haramo (CMIIW in spelling) placed it as a basal coelurosaur on his website. Rauhut wrote in his PhD thesis that B. lacks any characters linking it the Carcharodontosauridae and that it is very close to Deltadromeus. CARRANO 2002 considers Deltadromeus to be a ceratosaur

KURZANOV 1989 also placed it and Carcharodontosaurus saharicus as the closest allosaurids to the Tyrannosauridae, but he does not cite PAUL 1988, and he uses the following characters to determine their placement-

-Superior temporal fenestra merge above the temporals

I don't really understand this character as when I look at the skull of tyrannosaurids in dorsal view, they do not appear to merge, but they are very close together. Perhaps the translator made an error.

-Amphicoelous anterior dorsal vertebrae

Also in ceratosaurs, Szechuanosaurus? zigongensis, and nearly all coelurosaurs (incl. tyrannosaurids).

-Centrally located neural processes in the caudal vertebrae

I presume he's talking about the neural arches, but aren't these always located centrally?

-Acromial region of the scapula extremely wide

Evidentally, the scapula (HM 1912 VIII 60) was referred away from B., so this character cannot be used. I presume it was referred to Deltadromeus, because the figures in SERENO et al 1996 illustrate D. with this character.

-Triangular obturator process

This is supposed to be present in at least maniraptorans. It's not present in Sinosauropteryx or the Santana compsognathid (SMNK 2349 PAL).

He also considers Acrocanthosaurus atokensis to be a close relative to the Tyrannosauridae based on the following characters-

-Zygomatic process

Could someone clarify on this character?

-Wide postorbital edge

Which edge?

-Mature pleurocoels on the posterior dorsal vertebrae

Dorsal pleurocoels are present in at least Yanornis, Changchengornis, Confuciusornis, Deinonychus, Eoalulavis, Hesperornis, Ichthyornis, Longchengornis, Neuqueornis, Nomingia, Oviraptorids, Protopteryx, Rahonavis, Saurornitholestes, Cathayornis, the Spanish nestling, Nanshiungosaurus? brevispinus, Beipiaosaurus, Microvenator, tyrannosaurids, Caudipteryx, and possibly Archaeopteryx. They should be present in more taxa, but I'm not certain which.

BAKKER et al 1988 also consider A. atokensis to be a close relative to the Tyrannosauridae (and ornithomimids, troodontids, birds, and oviraptorids but not dromaeosaurids[!]) based on the following characters-

-paroccipital process very deep top-to-bottom at the root
-large excavation around the fenestra ovalis
-pneumatization of the paroccipital root

Are the latter two even present in tyrannosaurids or Acrocanthosaurus?

I also recommend looking at these-

That's all I know. Others will be able to provide more complete information and probably can correct some stuff in this post and answer some of my questions too. That's the beauty of the Dinosaur Mailing List. :D

Nick Gardner

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