The Ichthyosaurs

Ichthyosaurs, Greek for 'fish lizards' were large marine reptiles of the order Ichthyosauria. Their fossils have been found in rocks dating from 250 million  to 90 million years ago, in other words they were around for most of the Mesozoic period. They evolved from a group of unidentified land animals that returned to the sea. A more recent example of this kind of evolution is that of modern whales, although it is easier to trace the ancestry of whales than it is of Ichthyosaurs, partly because the whale fossil record is better preserved. For more information on whale evolution see my book, The Whale Trail of South Africa. Ichthyosaurs resembled modern dolphins – a good example of convergent evolution – developing fins and a streamlined shape to assist them in their new life in the oceans

The Triassic and early Jurassic was the hey-day of the Ichthyosaurs until they were knocked off their top spot by the Plesiosaurs. They became extinct in the Late Cretaceous for unknown reasons, but this is most probably related to the same causes that led to the extinction of the dinosaurs.

The first Ichthyosaurs were found in England during the early 1800s and the order Ichthyosauria was listed in 1834. Famous discoveries also took place in Germany and then in China, Mexico, USA, Norway, Tibet, Canada, Italy, Argentina and Columbia

There was great excitement when the first Ichthyosaur bones were discovered nearly two hundred years ago. Scientists and the public were enthralled by the strange shape of the creature with its large scleral rings which fitted into the eye sockets. People were then beginning to realise that huge amounts of time had gone by since these animals had swum in the ancient oceans, adding more to the sense of wonder about their discovery.

Ichthyosaurs ranged in length from one to sixteen metres. Their limbs had completely evolved into flippers to drive them through the Mesozoic oceans. Some of them even had a dorsal fin much like modern dolphins and sharks. Sharp teeth were often found in their pointed jaws which would have been very useful for catching prey. Some species had large bladelike teeth, presumably for taking on larger prey, much like modern killer whales or sharks. Large eyes improved vision when diving in deep water. They breathed air, gave birth to live young and possibly were warm blooded.

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