Knightia is an extinct genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of bony fish which lived in the fresh water

Fresh Water

Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...

 lakes and rivers of North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 during the Eocene

Eocene

The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...

 epoch

Epoch (geology)

An epoch is a subdivision of the geologic timescale based on rock layering. In order, the higher subdivisions are periods, eras and eons. We are currently living in the Holocene epoch...

. It was named by David Starr Jordan in 1907, in honor of the late University of Wyoming

University of Wyoming

The University of Wyoming is a land-grant university located in Laramie, Wyoming, situated on Wyoming's high Laramie Plains, at an elevation of 7,200 feet , between the Laramie and Snowy Range mountains. It is known as UW to people close to the university...

 professor Wilbur Clinton Knight, "an indefatigable student of the paleontology of the Rocky Mountains." It is the state fossil

State fossil

Most American states have made a state fossil designation, in many cases during the 1980s. It is common to designate one species in which fossilization has occurred, rather than a single specimen, or a category of fossils not limited to a single species....

 of Wyoming, and the most commonly excavated fossil fish in the world.

Description

Knightia belongs to the same taxonomic family as herring

Herring

Herring is an oily fish of the genus Clupea, found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Three species of Clupea are recognized. The main taxa, the Atlantic herring and the Pacific herring may each be divided into subspecies...

 and sardines

Sardine

Sardines, or pilchards, are several types of small, oily fish related to herrings, family Clupeidae. Sardines are named after the Mediterranean island of Sardinia, around which they were once abundant....

, and resembled the former closely enough that both Knightia alta and Knightia eocaena were originally described as species of herring.

Rows of dorsal and ventral scutes

Scute

A scute or scutum is a bony external plate or scale, as on the shell of a turtle, the skin of crocodilians, the feet of some birds or the anterior portion of the mesonotum in insects.-Properties:...

 ran from the back of the head to the medial fins. They had heavy scales, and small conical teeth. Their size varied by species: Knightia eocaena was the longest, growing up to 25 centimeters (10 inches), though most specimens are no larger than 15 centimeters. Knightia alta was shorter and relatively wider, with specimens averaging between 6 and 10 centimeters.

Predators

A small schooling

Shoaling and schooling

In biology, any group of fish that stay together for social reasons are said to be shoaling , and if, in addition, the group is swimming in the same direction in a coordinated manner, they are said to be schooling . In common usage, the terms are sometimes used rather loosely...

 fish, Knightia made an abundant food source for larger Eocene predators. The Green River Formation

Green River Formation

The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes. The sediments are deposited in very fine layers, a dark layer during the growing season and a light-hue inorganic layer in winter. Each pair of layers is called a varve and...

 has yielded many fossils of species preying on Knightia; specimens of Diplomystus

Diplomystus

Diplomystus is an extinct genus of non-clupeoid clupeomorph fish distantly related to modern-day extant herrings, alewives, and sardines. The genus was first named and described by Edward Drinker Cope in 1877. There are four species of Diplomystus: Diplomystus dentatus , D. birdii, D....

, Lepisosteus

Lepisosteus

Lepisosteus is a genus of gars in the family Lepisosteidae.There are four species:* Lepisosteus oculatus Winchell, 1864 * Lepisosteus osseus...

, Amphiplaga, Mioplosus

Mioplosus

Mioplosus is an extinct genus of prehistoric bony fish that lived from the early to middle Eocene.Very similar to today's perch, the Mioplosus is distinguished by its double dorsal fin and pointed teeth. It is thought to have been a solitary predator often attacking fish up to half of its own size...

, Phareodus

Phareodus

Phareodus is a genus of freshwater fish from the Eocene to the Oligocene of Australia and North America.This genus includes at least four species, P. testis and P. encaustus of North America, P. muelleri of Europe, and P. queenslandicus of Australia...

, Amia

Bowfin

The Bowfin, Amia calva, is the last surviving member of the order Amiiformes , and of the family Amiidae...

, and Astephus have all been found with Knightia in either their jaws or stomach.

Diet

Knightia likely fed on algae

Algae

Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

 and diatoms

Diatom

Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...

, as well as insects and the occasional smaller fish.