The bright midday sun glinted off the calm waters of the Inland Sea and silhouetted the long, sinuous form of a huge mosasaur lying motionless amid the floating tangle of yellow-green seaweed. At 20 years old, more than 30 feet in length, and weighing over a ton, the adult mosasaur was almost full grown and was much larger than any of the fishes or sharks that lived in the shallow seaway.