Ichthyosaurus is an extinct genus of ichthyopterygian marine reptiles, belonging to the order Ichthyosauria. The name means “fish lizard”, from Greek ikhthus (ἰχθύς), meaning “fish”, and sauros (σαῦρος), meaning “lizard”. They were the first large sea reptiles and dominated the seas for over 150 million years, from the Early Triassic to the Late Cretaceous periods. More than 200 species have been classified in the genus Ichthyosaurus, making it one of the most diverse groups of prehistoric animals known.
Ichthyosaurs were highly successful predators; their long, sharp teeth and powerful tails meant they could catch even fast-swimming prey. They ranged in size from less than a meter to over 20 meters in length, and their streamlined bodies would have helped them swim quickly through water. Some species had external flippers while others had none; some had dorsal fins while others did not. Despite their reptilian appearance, ichthyosaurs were warm-blooded: they had well-developed vascular systems that circulated blood around their bodies efficiently, keeping them at a constant temperature regardless of the surrounding water temperature. This adaptation would have given them an advantage over slower-moving cold-blooded predators such as plesiosaurs.
The first Ichthyosaurus fossils were found in England in 1814, and since then remains have been discovered on every continent except Antarctica. The majority of specimens come from Europe and North America, although finds have also been made in South America, Asia, Australia, and Africa. Many museums worldwide display examples of these fascinating creatures; one of the most famous is ‘Jurassic Mary’ – a complete skeleton unearthed near Peterborough in Cambridgeshire which now resides at Dorset County Museum.