Ocean Cruisers

Ichthyosaurs ("fish lizards") were seagoing reptiles whose streamlined bodies made them ideal for chasing fast-swimming prey. Their large bodies tapered at both ends, and they braked, steered, and stayed upright with help from flippers, a dorsal fin, and an upright tail fin. Like plesiosaurs, ichthyosaurs had to breathe air at the surface and may have had lizardlike ancestors who once lived on land, but they t i would have been helpless ashore. The price they paid for speed in the water was being unable to leave it. Ichthyosaurs were born, grew up, and died in the sea.

Dorsal fin

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Stenopterygius

Shark attack

Like dolphins, the living sea mammals they so closely resembled, ichthyosaurs could have leapt clear of the water for fun. But it seems unlikely that these unintelligent reptiles would have been jumping for joy. If they leapt at all, it is most likely that they did so to escape from attacking sharks or to shake off parasites.

Ichthyosaurus

An Ichthyosaurus and her young swim in a shallow sea where millions of years later western Europe would stand. Some ichthyosaur species grew five times longer than this 7 ft (2 m) creature, but none left more plentiful remains. After the first Ichthyosaurus was discovered in England, southern Germany's shale rocks yielded hundreds more skeletons of adults and young, making this one of the best known of all animals from the time of the dinosaurs.

The bones of the ear were huge to help pick up vibrations made by possible prey.

The bones of the ear were huge to help pick up vibrations made by possible prey.

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Seafood diet

Fast-moving squid, their prehistoric relatives belemnites and ammonites, and small fish were all snacks for the ichthyosaurs. Swift and agile, and capable of swimming at up to 25 mph (40 kmh), ichthyosaurs could outpace most prey. We know what ichthyosaurs ate from fish scales and belemnites' hooklets found in their stomachs and droppings.

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Squid

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Baby ichthyosaurus

As they were unable to lay eggs ashore, ichthyosaurs gave birth to their babies under water as whales do today. Scientists know this because partly formed babies were found inside some of the fossil ichthyosaurs that have been discovered. The skeletons of the babies were not broken up as they would have been if they had been swallowed and partly digested.

Fossil skeleton

Superbly preserved ichthyosaur fossils like this Stenopterygius include the body's outline. This shows that some ichthyosaur fins had no bones to support them. For instance, the spine's downcurved end strengthened only the lower part of the tail. In some fossils even pigment cells survive. These hint that Ichthyosaurus's skin was dark reddish-brown.

Eye socket

Nostrils

Eye socket

Nostrils

Skull

Ichthyosaurus's skull had long, narrow jaws crammed with sharp teeth for gripping slippery victims. The creature surfaced to breathe through nostrils in front of its eyes. Big sockets show the eyes were large, for hunting in the sea's dimly lit upper layers. A ring of bony plates around each eye helped muscles alter the eye's shape to focus on prey.

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Fossil finds

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