While dinosaurs roamed on land, what is now Peterborough was deep under the ocean. The ocean was teeming with life, enjoying the balmy climate similar to the Caribbean today.

Instead of large dinosaurs, huge marine reptiles were the rulers of the seas. They were every bit as diverse and ferocious as the giants on land. The largest of the marine reptiles were the long necked plesiosaurs and the short necked pliosaurs. Alongside them were the ichthyosaurs with their dolphin like bodies and armoured marine crocodiles. However, not all of the large marine creatures were reptiles. The fish Leedsichthys was one of the large creatures dominating the seas, growing up to 16m in length.

The Oxford Clay sea was an extremely rich environment with very high levels of nutrients which helped to support these large reptiles and fish. The animals interacted with each other in a complex series of ways each relying on the other, just as animals do in today’s oceans.

As in the Jurassic, plankton are eaten by fish that filter them through the water, and the fish themselves are eaten by sharks and larger predators. Sharks of the Jurassic are different to those found today, which would have fed on smaller fish and scavenged from carcasses floating in the water. Specimens of Leedsichthys are known with shark teeth embedded in them.

In addition to fish, the large ichthyosaurs, plesiosaurs and crocodiles would have feasted on ammonites and belemnites, along with other small molluscs such as bivalves. Bivalves lived on the seafloor, whilst the belemnites and ammonites would have used their shelled bodies to float and swim in the ocean.