Pentaceratops and Kosmoceratops Found in Campanian Cretaceous Alberta, Canada

The horned dinosaurs Pentaceratops and Kosmoceratops from the upper Campanian of Alberta and implications for dinosaur biogeography

Author:

Longrich

Abstract:

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.