Turtles have long been considered the most primitive of all living reptiles, in large part because their skulls lack temporal openings, which all later reptiles possess. The fossil history of turtles begins in the late Triassic. The first turtles were fairly large, terrestrial or semi-aquatic animals. They were thickly built and had armored tails. Anatomically, turtles have changed little since the late Triassic. Perhaps the most significant difference between primitive and modern turtles is that primitive turtles had teeth. Imagine a scientist makes a discovery that calls into question the theory presented above. What could this discovery be?