A REEVALUATION OF THE RELATIONSHIPS OF CAMPANIAN-AGED CROCODYLIANS OF WESTERN CANADA

Crocodylians formed an important part of the late Cretaceous paleocommunities of Laramidia. Although at least 5 taxa are known from the late Cretaceous (Campanian) sediments, ranging from Mexico to the North Slope of Alaska, much of the material is based on isolated scutes, vertebrae, and teeth frequently recovered from microvertebrate fossil assemblages. Most taxa are known from only a small number of skulls or diagnosable skull elements, with associated postcrania being rarely recovered. This is especially true for the basal crocodylomorphs collected from western Canada. This rarity of identifiable specimens complicates our understanding of the relationships within crocodylians of this region. Here we review the major crocodilian taxa from the Campanian of Laramidia and their phylogenetic relationships, providing the first detailed phylogeny of the basal crocodylomorphs to include Gilchristosuchus. This analysis supports the assessment of Gilchristosuchus as a derived non-eusuchian crocodylomorph presented by the original authors. This analysis also includes the first significant crocodylomorph specimen (a fragmentary skull) collected from the Foremost Formation (Campanian) of southern Alberta. Its relationship to other crocodylomorphs is poorly resolved within the present analysis.