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Pentaceratops and Kosmoceratops from upper Campanian of Alberta
A new paper:
Nicholas R. Longrich (2014)
The horned dinosaurs Pentaceratops and Kosmoceratops from the upper
Campanian of Alberta and implications for dinosaur biogeography.
Cretaceous Research 51: 292–308
The upper Campanian of the American Southwest has produced dinosaurs
that are unknown from the northern Great Plains and vice versa. This
has led to the idea that North America's Campanian dinosaur fauna was
characterized by high levels of endemism and distinct faunal
provinces. Here, two horned dinosaurs known from the Southwest,
Pentaceratops and Kosmoceratops, are described from southern Canada.
Pentaceratops aquilonius sp. nov. is represented by two frill
fragments from the uppermost Dinosaur Park Formation near Manyberries,
southeast Alberta. Features shared with Pentaceratops include large,
triangular epiparietals, an M-shaped parietal posterior bar, and an
epiparietal P1 that curls up and twists laterally. The Manyberries
specimens differ from Pentaceratops sternbergii and Utahceratops
gettyi in that the posterior bar is broader, emargination is weakly
developed, and P1 is directed dorsally, rather than anteriorly.
Phylogenetic analysis places P. aquilonius as sister to a clade
comprising P. sternbergii and Utahceratops. Kosmoceratops is
documented by a partial skull from Dinosaur Provincial Park.
Previously referred to Chasmosaurus, the skull exhibits derived
features inconsistent with this referral, including a reduced septal
flange, a caudally inclined narial strut, a triangular narial process,
a reduced frontal fontanelle, a weakly hooked rostral, and a narrow,
caudally inclined internal naris. Phylogenetic analysis recovers the
animal as sister to Kosmoceratops richardsoni, but differences in the
shape of the naris and nasal horn suggest that it likely represents a
distinct species. The presence of Pentaceratops and Kosmoceratops in
Canada argues against the idea of distinct northern and southern
faunal provinces, but the fact that they differ from their southern
relatives confirms that endemism was high in the Campanian. The
ability of dinosaur lineages to disperse long distances across North
America suggests that dinosaur distribution was not constrained by
geographic barriers, climate, or flora. Instead, dinosaur endemism may
result from competitive exclusion of immigrants by established
populations adapted to local environmental conditions.