A new crocodylian (Eusuchia) from the uppermost Cretaceous of Alberta, Canada

Abstract

Albertosuchus knudsenii gen. et sp. nov. is described on the basis of an incomplete skeleton from the lower part (uppermost Cretaceous) of the Scollard Formation, southern Alberta, Canada. It is probably a crocodyloid, the only Canadian representative of the group and also the sole crocodylian known during the latest Cretaceous in Canada. Within the Crocodyloidea, A. knudsenii is one of the most basal forms and shares a sister-group relationship with the European genus Arenysuchus. However, it needs to be emphasized that because of its incompleteness, phylogenetic relationships proposed here for A. knudsenii may change when better-preserved specimens are found. Albertosuchus knudsenii differs from other crocodyloids in having no premaxilla-maxillary notch, a very short mandibular symphysis with the involvement of the splenial, and an extremely deep hypapophysis on the last cervical and anterior dorsal vertebrae. The discovery of A. knudsenii may expand the geographical range of the Crocodyloidea into Canada during the Cretaceous. Crocodylians in the lower part of the Scollard Formation are of low diversity compared with that of the corresponding Hell Creek Formation of Montana and Lance Formation of Wyoming, both farther to the south in the USA.