By looking at fossils,scientists know that Tylosaurus had great 1.jaws and big 2.teeth. Studies of its 3.stomach contents show it ate fish, seabirds, and even sharks. Is used its long 4. Tail to push itself through the water and its two shorter 5. Fins to change direction. Tylosaurus was not related to the dinosaurs, but it lived and became extinct around the same time.