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Ugrunaaluk, new hadrosaurid from Late Cretaceous Arctic of Alaska (free pdf)



Ben Creisler
bcreisler@gmail.com

A new paper:

Hirotsugu Mori, Patrick S. Druckenmiller, and Gregory M. Erickson (2015)
A new Arctic hadrosaurid from the Prince Creek Formation (lower
Maastrichtian) of northern Alaska
Acta Palaeontologica Polonica (in press)
doi:http://dx.doi.org/10.4202/app.00152.2015
http://app.pan.pl/article/item/app001522015.html



The Liscomb bonebed in the Price Creek Formation of northern Alaska
has produced thousands of individual bones of a saurolophine
hadrosaurid similar to Edmontosaurus; however, the specific identity
of this taxon has been unclear, in part because the vast majority of
the remains represent immature individuals. In this study, we address
the taxonomic status of the Alaskan material through a comparative and
quantitative morphological analysis of juvenile as well several near
adult-sized specimens with particular reference to the two known
species of Edmontosaurus, as well as a cladistic analysis using two
different matrices for Hadrosauroidea. In the comparative
morphological analysis, we introduce a quantitative method using
bivariate plots to address ontogenetic variation. Our comparative
anatomical analysis reveals that the Alaskan saurolophine possesses a
unique suite of characters that distinguishes it from Edmontosaurus,
including a premaxillary circumnarial ridge that projects
posterolaterally without a premaxillary vestibular promontory, a
shallow groove lateral to the posterodorsal premaxillary foramen, a
relatively narrow jugal process of the postorbital lacking a
postorbital pocket, a relatively tall maxilla, a relatively gracile
jugal, a more strongly angled posterior margin of the anterior process
of the jugal, wide lateral exposure of the quadratojugal, and a short
symphyseal process of the dentary. The cladistic analyses consistently
recover the Alaskan saurolophine as the sister taxon to Edmontosaurus
annectens + Edmontosaurus regalis. This phylogenetic assessment is
robust even when accounting for ontogenetically variable characters.
Based on these results, we erect a new taxon, Ugrunaaluk kuukpikensis
gen. et sp. nov. that contributes to growing evidence for a distinct,
early Maastrichtian Arctic dinosaur community that existed at the
northernmost extent of Laramidia during the Late Cretaceous.