Relative dating of fossils and rocks
Mooneye: Mooneyes are scarce in the Green River Formation. Diplomystus: This fossil fish was not found in a mass-mortality layer (beds that contain hundreds of fish on one surface), which suggests that it did not die in a catastrophe.Like its modern relatives, it probably preferred river and stream environments and occasionally wandered into Fossil Lake. It most likely died from starvation or suffocation because it could not spit out the Knightia.
A fossil can consist of the preserved tissues of an organism, as when encased in amber, ice, or pitch, or more commonly of the hardened relic of such tissues, as when organic matter is replaced by dissolved minerals. Sellwood, 1992; British Geological Survey, Geology of the country around Brighton and Worthing, B. Lake, 1988; Geologists' Association Guide No.57, The Chalk of Sussex and Kent, R. Mortimore, 1997; Geological Conservation Review Series, British Upper Cretaceous Stratigraphy, R. Picture credits: Sponge by 'andrew104' at echinoid by 'topofbroadway' at lobster by David Galvan at shark by 'pugwash00' at References: A Dynamic Stratigraphy of the British Isles, A.