Fossil fish Knightia from Wyoming U.S.A.

Knightia is an extinct genus of clupeiform bony fishes from the herringidae family that lived in the freshwater lakes and rivers of North America during the Eocene. The genus was named in 1907 by David Starr Jordan, in tribute to the late University of Wyoming professor Wilbur Clinton Knight, "an indefatigable student of Rocky Mountain paleontology." Knightia is the state fossil of Wyoming and is the most excavated fossil fish in the world. Fossils include all remains and traces of plants and animals preserved in rocks. Contrary to popular belief, fossils do not necessarily have to be 'petrified'; many fossils are indeed not fossilized. Even in very old rocks, fossil remains have been found that have hardly changed. Nor is it true that fossils are always very old; many recent fossils are known, formed in periods that people can remember. Paleontology, the science that studies fossils, contributes to the study of rock sequence, a branch of geology called biostratigraphy. Because remains of life fossilize only under specific conditions, fossil information is limited and inherently "incomplete". People often associate the word fossil with the bones of dinosaurs or mammoths, and indeed the hard parts of an organism are the most likely to be preserved through fossilization. For vertebrates these are the bones and especially the teeth. The softer tissues of an organism are rarely preserved unless they are quickly covered by a layer that protects against rotting or feeding. It can be difficult to get a complete picture of the organism with only the hard parts. An example of this is the Conodonta, which for a long time were only known from their tooth-like fossils.