''Knightia'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

clupeid Clupeidae is a family of clupeiform ray-finned fishes, comprising, for instance, the herrings and sprats. Many members of the family have a body protected with shiny cycloid (very smooth and uniform) scales, a single dorsal fin, and a fusiform ...

bony fish Osteichthyes ( ; ), also known as osteichthyans or commonly referred to as the bony fish, is a Biodiversity, diverse clade of vertebrate animals that have endoskeletons primarily composed of bone tissue. They can be contrasted with the Chondricht ...

that lived in the

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...

lakes and rivers of

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

and

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

during the

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided b ...

. The genus was erected by

David Starr Jordan David Starr Jordan (January 19, 1851 – September 19, 1931) was the founding president of Stanford University, serving from 1891 to 1913. He was an ichthyologist during his research career. Prior to serving as president of Stanford Universi ...

in 1907, in honor of the late

University of Wyoming The University of Wyoming (UW) is a Public university, public land-grant university, land-grant research university in Laramie, Wyoming, United States. It was founded in March 1886, four years before the territory was admitted as the 44th state, ...

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

state fossil Most states in the US have designated a state fossil, many during the 1980s. It is common to designate a fossilized species, rather than a single specimen or a category of fossils. State fossils are distinct from other state emblems like state d ...

Wyoming Wyoming ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States, Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho t ...

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

Taxonomy

''Knightia'' belongs to the same taxonomic family as

herring Herring are various species of forage fish, belonging to the Order (biology), order Clupeiformes. Herring often move in large Shoaling and schooling, schools around fishing banks and near the coast, found particularly in shallow, temperate wate ...

and

sardine Sardine and pilchard are common names for various species of small, oily forage fish in the herring suborder Clupeoidei. The term "sardine" was first used in English during the early 15th century; a somewhat dubious etymology says it com ...

s, and resembled the former closely enough that both ''Knightia alta'' and ''Knightia eocaena'' were originally described as species of true herring in the genus ''

Clupea ''Clupea'' is genus of planktivorous bony fish belonging to the family Clupeidae, commonly known as herrings. They are found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Two main ...

''. As with modern-day clupeids, ''Knightia'' spp. likely fed on

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

and

diatom A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...

s, as well as insects and occasionally smaller fish. In a 2022 paper, researchers announced they had detected biological residues in ''Knightia'' fossils from the

Green River Formation The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day Green River (Colorado River), Green River in Colorado, Wyoming, and Utah. The sedimen ...

. The genus is also known from two separate species described from China dating to the Eocene and Late Cretaceous respectively. The Eocene species ''Knightia bohaiensis'' was described in 1985 from the Bohai Bay Basin region, while ''"Knightia" yuyanga'' was first identified as Eocene when described from the Itu region in 1963. The age of ''"K." yuyanga'' has been revised with the placement of the species' type locality in the Late Cretaceous Paomagang Formation. Additionally the species placement in ''Knightia'' has been questioned, and the species is now treated as "Clupeid ''incertae sedis''". The Cretaceous genus '' Ellimma'' from Brazil was formerly synonymized into ''Knightia'' as ''Knightia branneri'' by Schaeffer (1947). This placement was rejected by Grande (1982) and subsequent authors, and the species moved back to '' Ellimma branneri''.

Anatomy

In ''Knightia'' fish, rows of

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

and

ventral Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

scute A scute () or scutum (Latin: ''scutum''; plural: ''scuta'' "Scutum (shield), shield") is a bony external plate or scale overlaid with horn, as on the shell of a turtle, the skin of crocodilians, and the feet of Bird anatomy#Scales, birds. The ter ...

s run 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 cm (10 in), though most specimens are no larger than 15 cm. ''K. alta'' was shorter and relatively wider, with specimens averaging between 6 and 10 cm.

Predators

A small

schooling A school is the educational institution (and, in the case of in-person learning, the building) designed to provide learning environments for the teaching of students, usually under the direction of teachers. Most countries have systems of fo ...

fish, ''Knightia'' made an abundant food source for larger Eocene predators. The

has yielded many fossils of larger fish species preying on ''Knightia''; specimens of ''

Diplomystus ''Diplomystus'' is an extinct genus of freshwater and marine clupeomorph fish distantly related to modern-day extant herrings, anchovies, and sardines. It is known from the United States, China, and Lebanon from the Late Cretaceous to the middle ...

'', ''

Lepisosteus ''Lepisosteus'' (from Greek ''lepis'' (), 'scale' and ''osteon'' (), 'bone') is a genus of gars in the family Gar, Lepisosteidae. It contains four extant species, found throughout eastern and central North America. It is one of two extant gar gen ...

'', '' Amphiplaga'', '' Mioplosus'', '' Phareodus'', '' Amia'', and '' Astephus'' have all been found with ''Knightia'' in either their jaws or stomachs.Grande, L. 1980. The paleontology of the Green River Formation, with a review of the fish fauna. Wyoming Geol. Surv., Bull. 63, pp. 85.

Gallery

References

External links

* * {{Taxonbar, from=Q288279 Clupeidae Eocene fish of North America Symbols of Wyoming Prehistoric ray-finned fish genera Taxa named by David Starr Jordan Green River Formation