By | September 9, 2016

The ichthyosaurs were the largest sea-dwelling reptiles of all time. They evolved from land-living reptiles that adapted so well to life in the sea that some species came to resemble dolphins. Like dolphins, they fed, bred, and gave birth in water but had to return to the surface to breathe air.


Key features
■ Large eyes for good underwater vision
■ Flippers for steering and balance
■ Vertical tail fin
■ Gave birth to live babies rather than laying eggs
■ Lungs for breathing air

Ichthyosaurs lived from about 245 million years ago (Triassic Period) to nearly 90 million years ago (Cretaceous Period).

Shonisaurus (SHON-ee-sore-us)


When: 225–208 million years ago (Late Triassic)

Fossil location: N. America

Habitat: Oceans

Length: Up to 70 ft (20 m)

Diet: Fish, squid

Shonisaurus was like a cross between a whale and a dolphin, with an enormous body but a long, slender snout. Giant eyes and toothlessness in adults suggest it was a deep-diving squid hunter. One whale-sized specimen found in Canada was 70 ft (20 m) long—the largest marine reptile ever found.

Ophthalmosaurus (off-THAL-mo-SORE-uss)


When: 165–150 million years ago (Late Jurassic)

Fossil location: Europe, N. America, Argentina

Habitat: Oceans

Length: 16 ft (5 m)

Diet: Fish, squid, mollusks

Ophthalmosaurus means “eye lizard.” This ichthyosaur had the largest eyes relative to body size of any prehistoric animal. The eyes were as big as grapefruits and almost filled the skull. Ophthalmosaurus could probably see well in the dark and may have used its extraordinary vision to hunt in the depths of the sea. If so, it must also have been good at holding its breath for long periods on its trips into the deep.

Mixosaurus (MIX-oh-SORE uss)



When: 230 million years ago (Middle Triassic)

Fossil location: N. America, Europe, Asia

Habitat: Oceans

Length: Up to 3 ft 3 in (1 m)

Diet: Fish

Mixosaurus was one of the smallest ichthyosaurs. It swam by beating its tail from side to side, perhaps using bursts of speed to take shoals of fish by surprise. It caught prey in a long, narrow snout, which was lined with sharp teeth. Fossils of Mixosaurus have been found all over the world, indicating that the species lived throughout the oceans.

Ichthyosaurus (ICK-thee-oh-SORE-uss)


When: 190 million years ago (Early Jurassic)

Fossil location: British Isles, Belgium, Germany

Habitat: Oceans

Length: 6 ft (1.8 m) long

Diet: Fish

Ichthyosaurus was a small, slim-snouted ichthyosaur. It had dozens of sharp, needlelike teeth and used them to catch squid or other kinds of mollusks. Studies of the ear bones of Ichthyosaurus show that it didn’t have the highly sensitive hearing that dolphins have and couldn’t detect objects in the water by using echoes (echolocation).




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