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Peterborough Under Water

165 million years ago


Peterborough was much closer to the equator in Jurassic times and a shallow sea covered the area. Together with warmer global temperatures, the local climate would have felt as balmy as the Bahamas. In the 145 million years since the Jurassic Period, the continents have moved hundreds of miles. Ever since the Earth formed, the rocky plates on its surface have moved around very slowly, powered by the heat in the planet’s core. Today, the continents continue to move as they collide and separate very slowly. Peterborough’s Jurassic sea was packed with creatures of all sizes, from microsopic to monstrous. The small fish, ammonites and belemnites feasted on shoals of plankton. They in turn became food for larger creatures. At the top of the food chain were the large ichthyosaurs, plesiosaurs, pliosaurs and crocodiles. The shallow sea supported a huge variety of fish of all sizes and shapes, adapted for life at different depths in the water. Near the surface, shoals of fast-swimming Caturus hunted smaller fish. The vast Leedsichthys – the biggest fish ever known – cruised harmelssly among them, gulping in water and filtering plankton to eat. When these creatures died they sank to the bottom of the sea where some of them became fossilised. Peterborough Museum houses a magnificent collect of these fossils.

Pachycostasaurus dawnii

150 million years ago


This fossil was found locally at the brick pits in Kings Dyke in 1994. Scientists studied the bones and found that this was a unique beast: a new type of pliosaur not found before. Pliosaurs were a group of plesiosaurs, skilled in ambush and the fast pursuit of their prey.  They had thin bones which were designed to reduce the weight of their skeletons. Pachycostasaurus Dawnii was found to have elements of its skeleton which were thickened rather than thin.  This has suggested to scientists that it would not have been a fast swimmer, but instead a slow stable swimmer. When new types or species are found, the scientists that have described them also get the chance to name them. Pachycostasaurus dawnii was named after its discoverer; local palaeontologist, Alan Dawn.