Two elasmosaurid plesiosaur specimens have been recovered from rocks of the San Francisquito Formation(?) in Cajon Pass, California. Some invertebrate fossils and palynomorphs from the San Francisquito Formation(?) here indicate a Paleocene age, but no direct association of Paleocene fossils and the plesiosaur fossils can be demonstrated. Therefore, the Cajon Pass plesiosaurs are most reasonably considered Late Cretaceous.