This page is under water. None of these were dinosaurs: they were other reptiles that had gone back to the sea. Move your pointer and one will swim after you. Choose a different one at the bottom, and tap the notes to open them.
Reptiles, fish and mammals have all arrived at the same streamlined shape for fast swimming.
A ring of bone supported each huge eye. It could see in dim, deep water.
In 1811 Mary Anning, aged twelve, and her brother found the first skeleton to be studied by scientists.
Fossils show mothers with young inside them, and one giving birth.
It may have reached 25 miles an hour.
Fossil droppings, full of fish scales and squid hooks, were first recognised from ichthyosaurs.
Meet them all
Fish lizard · IK-thee-oh-SORE-us
A sleek sea reptile shaped like a dolphin, with a long toothy snout, huge eyes, four flippers and a fish-like tail.
Near to lizard · PLEE-see-oh-SORE-us
A sea reptile with a small head, a long neck, a broad body, four long flippers and a short tail.
Smooth-sided tooth · LIE-oh-PLOOR-oh-don
A powerful sea reptile with a huge head, a short neck and four big flippers.
Lizard of the Meuse · MOE-za-SORE-us
A gigantic swimming lizard with a long head, four flippers and a tail with a fluke like a shark's.
Thin-plate lizard · el-LAZZ-moe-SORE-us
A plesiosaur with a tiny head on an astonishingly long neck, a broad body and four flippers.
Ruler turtle · AR-kell-on
The largest turtle ever: the size of a small car, with a leathery shell and huge front flippers.
Good to know
No dinosaur lived in the sea. These were separate families of reptile.
All of them breathed air, like whales and turtles today.
Fossils show ichthyosaurs and plesiosaurs giving birth to live young in the water.
Mary Anning found the first complete ichthyosaur and plesiosaur skeletons in the cliffs of Lyme Regis.
Chemical studies suggest several of them kept their bodies warm, as tuna and whales do.
Plesiosaurs and mosasaurs died out in the same extinction, 66 million years ago. Turtles survived.
Sea and sky: 1 more place
Real fossils, skeletons and museum models of the animals on this page. Tap one to see it bigger.
Photos are from Wikimedia Commons and are used under free licences. They have been resized, and cropped where they appear in link previews. Open a photo to see who took it.
For more than 150 million years the top hunters in the ocean were reptiles. Whales, seals and dolphins only arrived after they had gone.
Back to the topThese live somewhere else: choosing one takes you to their page.
Animals from other periods live on their own pages: choose another.