The Christian Malford exceptionally preserved fauna occurs in the Peterborough Member of the Oxford Clay Formation (Callovian, Middle Jurassic), According to the amateur palaeontologist Joseph Chaning Pearce writing in 1841 the best preserved fossils came from a 1.8m thick part of the succession consisting of ‘four or five bands of laminated clay alternating with sandy clay’. They occur at a level within the phaeinum Subzone of the athleta Zone. Discovered early in the 1840s during the construction of the Great Western Railway and was still being collected up until 1854.