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Aguja tyrannosauroid from Texas



From: Ben Creisler
bcreisler@gmail.com

A new online paper:


Thomas M. Lehman and Steven L. Wick (2013)
Tyrannosauroid dinosaurs from the Aguja Formation (Upper Cretaceous)
of Big Bend National Park, Texas.
Earth and Environmental Science Transactions of the Royal Society of
Edinburgh  (advance online publication)
DOI: http://dx.doi.org/10.1017/S1755691013000261
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9015642&fulltextType=RA&fileId=S1755691013000261

Rare remains of tyrannosauroid dinosaurs from the Aguja Formation in
West Texas indicate the presence here of a relatively gracile species,
comparable in form and adult size to Appalachiosaurus or subadult
albertosaurines, Gorgosaurus and Albertosaurus. Histologic analysis of
one of the specimens indicates that the Aguja tyrannosaur attained an
adult size substantially smaller than adult albertosaurines (700 kg,
6·5 m body length). The frontal bone is narrow with a wide orbital
slot and a bipartite joint for the postorbital, features thought to be
diagnostic of Albertosaurinae; but there is a tall sagittal crest and
reduced parietal wedge separating the frontals on the midline,
features thought to be diagnostic of Tyrannosaurinae. The tall
sagittal crest may be a synapomorphy of Tyrannosaurinae, and the Aguja
tyrannosaur is herein referred to that clade. However, the unique
combination of character states exhibited by the frontal prevents
confident attribution to any known species. The Aguja tyrannosaur
provides further evidence that North American Campanian
tyrannosauroids were remarkably diverse for such large predators, and
that each species was apparently endemic to a relatively small
geographic province.