Long before dolphins first appeared, the seas of the Jurassic were home to reptiles that had evolved a remarkably similar body shape and lifestyle. These were the ichthyosaurs. One type of ichthyosaur, Stenopterygius, spent its life in the open ocean, where it hunted fish, cephalopods, and other marine animals.
■ When: Early to mid Jurassic
■ Fossil location: Argentina, UK, France, Germany
■ Habitat: Shallow oceans
■ Size: 13 ft (4 m) long
Like its close relative Ichthyosaurus, Stenopterygius was a dolphinlike reptile adapted to catching fish in its tooth-filled snout. Its streamlined shape and muscular fins suggest it could achieve a top speed of perhaps 60 mph (100 kph), enabling it to blast into shoals of fish like a torpedo and snatch prey in the resulting confusion.