Welcome to the Jurassic period, which existed between 145 and 200 million years ago. With the supercontinent Pangaea continuing to separate, more and more big watery lagoons were forming, and along with the new oceans, were teeming with life – from the tiny to the monstrous!
Dinosaurs didn’t live in the sea but all of the first creatures to appear on earth did. On the seabed you would see sponges that looked like squishy lumps, tiny corals that were building huge rocky reefs and starfish . These animals had been around for millions of years before dinosaurs and are just like those you’d find on the beach today.
An Ammonite is a close relative of squid and octopuses whose ancestors had already been around for 150 million years before the dinosaurs first appeared. They came in all sizes – some were as big as two metres wide. The hard shell protected its squishy body, and its tentacles were used for swimming and catching food.
Plesiosaurs were sea creatures with tubby bodies, four flippers and a short tail. Some had long slender necks and small heads, while others had huge heads but short, powerful necks. They were both agile and terrifying. Some of the biggest, like Liopleurodon, were at least 10 metres long – that’s nearly as long as a bus. They had sharp teeth that could be over 30 cm long. They were the top predators in the ocean – feeding on whatever marine reptiles and fish they could grab.
Away from the oceans, in the watery lagoons, lived even more sea monsters! Fast fish eaters like the Ichthyosaurs were dolphin-like creatures with a tail fin and four flippers.
Temnodontosaurus was a massive Ichthyosaur – over 10 metres long with huge eyes that helped him see in the gloomy water. Since Ichthyosaurs didn’t have gills, they couldn’t breathe underwater and had to come to the surface to breath – just like whales do today.