The first specimen was found in 1865 by fossil collector John Griffiths on the shoreline at Folkestone. The stratum was Cambridge Greensand, a formation in the Lower Cretaceous of southern England. At the time England was part of a huge tropical river delta, and the Greensand was laid down just offshore. It seems that dinosaurs were on the shoreline or the river delta, and sometimes their bodies washed out to sea.