First records of a Plesiosaurian (Reptilia: Sauropterygia) and an Ichthyosaur (Reptilia: Ichthyosauria) from Yukon, Canada

Abstract

An isolated centrum collected ex situ from marine shales of the Lower Cretaceous (Albian) Arctic Red Formation along the Road River represents the first documented occurrence of a plesiosaurian from Yukon. This centrum represents the northernmost occurrence of plesiosaurians in the Western Interior Sea of North America prior to the establishment of the first continuous seaway (Western Interior Seaway) connecting the Boreal and Tethyan seas. Additionally, this centrum is potentially the second-oldest elasmosaurid specimen known from North America. A second centrum, collected along the Beaver River, is likely derived from the Lower Cretaceous (Lower Albian) Garbutt Formation exposed farther upstream. It represents the first report of an ichthyosaur from Yukon. Additionally, six associated ribs collected from the Arctic Red Formation along the Peel River may also belong to a marine reptile; however, poor preservation of these ribs prevents a definitive taxonomic assignment.