Fossil fish from Utah (Medium size)

Knightia is an extinct genus of Clupeid Clupeiformes bony fish which lived during the Eocene in freshwater lakes and rivers of North America. The race was founded by David Starr Jordan in 1907, in honor of the late University of Wyoming Professor Wilbur Clinton Knight, "a tireless student of paleontology of the Rocky Mountains." It is the fossil state of Wyoming, and the most excavated fossil fish in the world.

Among fossils means all residues and traces of plants and animals preserved in rock. Although it is often thought, fossils do not have to be 'petrified'. Many fossils are indeed not petrified. Even in very old rocks are known fossil remains that have hardly changed. Furthermore, many believe that fossils always very old. Again, this is not right. There are many very early fossils known to occur in people known periods. The science that studies fossils is called paleontology. This area of knowledge helps in the investigation of the sequence of rocks, a branch of geology called biostratigraphy. As remnants of life fossilize only under specific circumstances, the fossil information is limited and, by definition, "incomplete". At the word fossil think one often to the bones of dinosaurs and mammoths, and it is true that the hard parts of an organism are most likely to be preserved by fossilisation. For vertebrates be that the bones and particularly the teeth. The softer tissues of the organism remain only in special cases saved and are therefore much rarer. Softer fabrics are only saved if they get buried quickly under a layer that shields them against any form of decay or damage. With only the hard parts is sometimes difficult to form a clear picture of the entire organism. A good example is the conodont that were found a long time in large numbers, but were only known from its teeth. Only when there is a printout of the remainder of such animal was found, it appeared that this was a primitive form of stem Chordata. In other animal groups are often other hard parts, such as fossilized shells. There are a number of special forms of fossilisation. In amber, for example, sometimes entrapped insects found complete, because the resin from which the amber was created, provides a good barrier against oxidation. This applies on a larger scale also tar pits. Near the US city of Los Angeles is a good example in the La Brea tar pits. Of animals that were trapped in the tar pit, the bones were often kept very well. Moreover, the trapped animals drew often predators, which also became entangled. In this way, a "graveyard bones" are formed during the Pleistocene. In clays that are very well preserved fossils found deposited in stagnant anoxic water. The absence of oxygen plants fossilize it particularly well. Very often it is not the whole water column oxygen but only the lower part. Such layered water thus has a normal oxygen content in the upper layer. In the upper layer will kill organisms which then sink down and then end up in an oxygen-free environment where they are kept. Also living organisms may end up inadvertently in the bottom anoxic layer which they die and fossilize. In such a deposition fish are sometimes kept in a cramped manner suggesting suffocation. A well-known rock with such fossils is the "Kupferschiefer 'from the Rotliegend in central Germany. In addition to moieties which are derived from organisms themselves are also traces by organisms which are active or passive made counted among the fossils. They include coprolites (fossilized feces) and trace fossils like footprints and dig corridors. Of trace fossils, it is not always possible to determine what kind of animal they are derived. They therefore often have their own taxonomic designation.