Paleontologists from Manchester University found 205-million year-old jaw bone of a prehistoric reptile belongs to 'one of the largest animals ever' (bigger than the blue whale). It's the jaw bone of giant Ichthyosaur. Now, when dinosaurs were hip-hopping on the land few of their cousins jumped into the sea and became the aquatic reptiles. Those few cousins appeared like a huge fish with limbs modified into flippers and tail with a caudal fin, they had a shark like fin on the back (dorsally), jaws with pointed beak with sharp teeth. Yeah, those were Ichthyosaur.