The hunt for dinosaur fossils has been undertaken by both professional and amateur prospectors since the mid-1800's. As it is in the search for all manner of buried treasure, the key to success lies in narrowing the search field and keen observation. Primarily, dinosaur fossils are found in terrestrial sedimentary deposits associated with ancient lake and river systems. Characterised by vast landscapes of exposed sediment beds, the continental interior areas (e.g. the Badlands of North America and the Gobi Desert of Mongolia) have yielded exceptional dinosaur finds. However, due to dinosaurs' pandemic (wide) distribution, fossils have been discovered in Late Triassic (250myr) to End Cretaceous (65myr) sediments from various locations.One example of a marginal marine palaeoenvironment with a dinosaur fossil bearing horizon is in the 11m x1m clay (lower Jurassic) lens exposed at the Hornsleasow Quarry site in Gloucestershire, England. Excavation of the site uncovered the remains of a Cetiosaurus (saurapod) dinosaur which is interpreted as having been initially deposited on the flood plain during a time of low sea level. The Cetiosaur remains could then have been washed into a hollow during a flood event (fresh water). According to Roger Vaughan, the Geological Advisor of the excavation team (presently with the Bristol City Museum), the impetus to excavate came from the initial finds of a Cetiosaur hip bone (photo) and vertebrae by a local enthusiast.