Megaherbivorous dinosaur turnover in the Dinosaur Park Formation (upper Campanian) of Alberta, Canada

Ongoing research into the biostratigraphy of the upper Campanian Dinosaur Park Formation (DPF) of Alberta has demonstrated that megaherbivorous dinosaur taxa (ankylosaurs, ceratopsids, hadrosaurids) are not homogeneously distributed throughout the unit. This has compelled proposals of different, informal assemblage zone schemes, and the hypothesis that faunal turnover was driven by environmental change associated with marine transgression. The current study tests previous zonation schemes in addition to the hypothesis of turnover pulses in the DPF. Clustering and ordination methods are used to demonstrate the existence of two broad assemblage zones within the DPF, each of which lasted ~ 600 Ka: a lower zone characterized by the presence of the ceratopsid Centrosaurus apertus and the hadrosaurids Corythosaurus, and an upper zone characterized by the presence of the ceratopsid Styracosaurus albertensis and the hadrosaurid Prosaurolophus maximus. These zones can be further sub-divided, based on the distributions of rarer or shorter-lived ankylosaur, ceratopsid, and hadrosaurid species, into ~ 300 Ka sub-zones. Canonical correspondence analysis is used to explore the association between the turnover of the megaherbivorous dinosaurs and various palaeoevironmental proxies. Megaherbivorous dinosaur turnover most closely corresponds to that of fossil palynomorphs. However, none of the palaeoenvironmental proxies explains dinosaur distribution better than a simple time gradient, suggesting that dinosaur turnover was not inextricably linked to environmental change as predicted by the turnover pulse hypothesis.