Alexeyisaurus is the stratigraphically oldest named possible plesiosaur. It was named and described by Sennikov and Arkhangelsky (2010) as an elasmosaurid plesiosaur from the Late Triassic of Franz Josef Land, Russia. This would be highly unusual because the oldest definitive elasmosaurid plesiosaurs are otherwise restricted to the Cretaceous Period. The holotype material of…