Ichthyosaurs were marine reptiles that were plentiful in the
Triassic and Jurassic periods (252-145 million years ago) but became rarer in
the late Jurassic and died out during the Cretaceous period, about 66 million
years ago.
The first ichthyosaurus fossil was found in 1811 by the
fossil hunter Mary Anning in the cliffs near her home in Lyme Regis, Dorset,
England. Since then, ichthyosaur remains have been found in many parts of the
world including North and South America, Europe, Russia, India and Australia.
Ichthyosaurs (the name means “fish lizard”) looked similar
to both modern sharks, which are fish, and dolphins, which are mammals. Some fossils
have been found with embryos inside them, showing that they gave birth to live
young, like mammals but unlike fish.
They resembled fish by waving their tails from side to side
to swim. Their large ear bones suggest that they were able to pick up
underwater vibrations caused by their prey.
Ichthyosaurus (a commonly found ichthyosaur) could grow up
to two metres (6.6 feet) long and has been estimated to have weighed up to 90
kg (198 pounds). A less common ichthyosaur was Shastasaurus which could grow up
to 20 metres (65.6 feet) long and perhaps weighed around 25 tonnes.
© John Welford
