Alienochelys selloumi, a sea turtle from the Late Cretaceous of Morocco (70-66 mya). Although only known from a single skull, it was probably around 2-2.5m long (6′6″- 8′2″), and was closely related to both the modern leatherback turtle and the giant Archelon – and so it wouldn’t have had a solid shell but instead a leathery skin-covered carapace.
But that one skull was also incredibly weird. While most turtles have pointed beaks, Alienochelys had a blunt squared-off face, sort of “pug-nosed”, with its nostrils set high up between its eyes. It seems to have been specialized for crushing hard-shelled prey between the wide flat grinding surfaces of its beak, more similar to the jaws of rays than those of other turtles.