Ankylosaurid diversity in the Late Cretaceous of Alberta and Montana

[Ben Creisler <bcreisler@gmail.com>]

From: Ben Creisler
bcreisler@gmail.com

A new paper in PLoS ONE:

Victoria M. Arbour & Philip J. Currie (2013)
Euoplocephalus tutus and the Diversity of Ankylosaurid Dinosaurs in
the Late Cretaceous of Alberta, Canada, and Montana, USA. PLoS ONE
8(5): e62421. doi:10.1371/journal.pone.0062421
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062421


Few ankylosaurs are known from more than a single specimen, but the
ankylosaurid Euoplocephalus tutus (from the Late Cretaceous of
Alberta, Canada and Montana, USA) is represented by dozens of skulls
and partial skeletons, and is therefore an important taxon for
understanding intraspecific variation in ankylosaurs. Euoplocephalus
is unusual compared to other dinosaurs from the Late Cretaceous of
Alberta because it is recognized from the Dinosaur Park, Horseshoe
Canyon, and Two Medicine formations. A comprehensive review of
material attributed to Euoplocephalus finds support for the
resurrection of its purported synonyms Anodontosaurus lambei and
Scolosaurus cutleri, and the previously resurrected Dyoplosaurus
acutosquameus. Anodontosaurus is found primarily in the Horseshoe
Canyon Formation of Alberta and is characterized by ornamentation
posterior to the orbits and on the first cervical half ring, and wide,
triangular knob osteoderms. Euoplocephalus is primarily found in
Megaherbivore Assemblage Zone 1 in the Dinosaur Park Formation of
Alberta and is characterized by the absence of ornamentation posterior
to the orbits and on the first cervical half ring, and keeled medial
osteoderms on the first cervical half ring. Scolosaurus is found
primarily in the Two Medicine Formation of Montana (although the
holotype is from Dinosaur Provincial Park), and is characterized by
long, back-swept squamosal horns, ornamentation posterior to the
orbit, and low medial osteoderms on the first cervical half ring;
Oohkotokia horneri is morphologically indistinguishable from
Scolosaurus cutleri. Dyoplosaurus was previously differentiated from
Euoplocephalus sensu lato by the morphology of the pelvis and pes, and
these features also differentiate Dyoplosaurus from Anodontosaurus and
Scolosaurus; a narrow tail club knob is probably also characteristic
for Dyoplosaurus.