The place:
The Oxford Clay lies under much of southern England but only outcrops at the surface in a relatively narrow band, running across the country from Weymouth to the Yorkshire coast. The best sites have been the numerous quarries around Oxford and Peterborough where the clay is extracted for brick-making.

The finds:
The Oxford clay is full of fish and invertebrate fossils including the huge fish Leedsichthys and numerous types of ammonite. However it is for the well-preserved marine reptiles that it is most famous. Skeletons of several species of ichthyosaur, including Ophthalmosaurus have been found, as well as the plesiosaurs, Cryptoclidus and Liopleurodon. More rare are the remains of dinosaurs whose carcasses must have drifted out to sea.

The environment:
In the Late Jurassic period the Oxford clays were wholly marine and were deposited in relatively deep water. However the presence of occasional dinosaur fossils indicates that land could not have been far away.

The people who found the fossils:
One name will always associated with the Oxford Clay - Alfred Leeds - an amateur fossil collector who farmed land near Peterborough. From 1860 to 1915, he regularly patrolled the local quarries and his finds include many ichthyosaurs and plesiosaurs. Most of his finds went to the Natural History Museum in London and Glasgow University.