In theory could the plesiosaurus have been alive in the triassic?

Genuine question because there is evidence that dates it back to the start on the jurassic pretty close to the late triassic and there are plesiosaurus decendants that lived during the triassic so is it really far fetched to question if the plesiosaurus lived in the triassic aswell? ( im also looking for any reason to add plesiosaurus to my triassic park in jwe)