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[dinosaur] Tyrannosauroid metatarsus from Merchantville Formation of New Jersey (free pdf)

Ben Creisler

A new paper in open access:

Chase D Brownstein (2017)
A Tyrannosauroid Metatarsus from the Merchantville Formation of New Jersey increases the diversity of non-Tyrannosaurid Tyrannosauroids on Appalachia.
PeerJ Preprints 5:e3097v1 
doi: https://doi.org/10.7287/peerj.preprints.3097v1

For almost the entirely of the latter half of the Cretaceous, the continent of North America was divided into two sections, Laramidia in the west and Appalachia in the east. Unfortunately, this latter landmass recorded only a sparse fossil record of dinosaurs, obscuring those forms which must have occupied the eastern portion of North America during this time. Appalachian dinosaur faunas, though obscure, do seem to be different in composition from Laramidian ones. One particular element of Appalachian faunas that has attracted significant attention are the non-tyrannosaurid tyrannosauroids of the continent. Tyrannosauroids on Appalachia, though represented by at least two taxa (Appalachiosaurus montgomeriensis and Dryptosaurus aquilunguis), as well as many partial and fragmentary skeletons and elements, are nevertheless poorly know when compared to their western contemporaries. Here, one specimen, the partial metatarsus of a tyrannosauroid from the Campanian Merchantville Formation of New Jersey, is described in detail. The specimen may be differentiated from Appalachiosaurus montgomeriensis, Dryptosaurus aquilunguis, and an unnamed specimen from the Maastrichtian of New Jersey by several notable morphological features outside the spectrum of individual variation, as well as by factoring in biogeographical considerations. The new specimen thus has significance for representing a new morphotype of tyrannosauroid from Appalachia, suggesting greater diversity of the clade on the landmass. Because of this, tyrannosaur diversity in the Campanian of Appalachia was compared to the diversity of tyrannosaurs in Laramidia during the same period to analyze the similarities and differences between the biogeography of tyrannosaurs on each landmass. The results suggest that Appalachian non-tyrannosaurid tyrannosauroids experienced a similar amount of diversity to tyrannosaurids in Laramidia during the Campanian.