| Knightia | |
|---|---|
 | |
| Knightia eocaena specimen | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Clupeiformes |
| Family: | Clupeidae |
| Subfamily: | Pellonulinae |
| Genus: | †Knightia Jordan 1907 |
| Type species | |
| Knightia eocaena Jordan, 1907 | |
| Species | |
| Synonyms | |
Knightia is anextinctgenus ofclupeidbony fish that lived in thefreshwater lakes and rivers ofNorth America andAsia during theEoceneepoch. The genus was erected byDavid Starr Jordan in 1907, in honor of the lateUniversity of Wyoming professor Wilbur Clinton Knight, "an indefatigable student of the paleontology of the Rocky Mountains."[1] It is the officialstate fossil ofWyoming,[2] and the most commonly excavated fossil fish in the world.[3]
Knightia belongs to the same taxonomic family asherring andsardines, and resembled the former closely enough that bothKnightia alta andKnightia eocaena were originally described as species of true herring in the genusClupea.
As with modern-day clupeids,Knightia spp. likely fed onalgae anddiatoms, as well as insects and occasionally smaller fish.[4] In a 2022 paper, researchers announced they had detected biological residues inKnightia fossils from theGreen River Formation.[5]
The genus is also known from two separate species described from China dating to the Eocene and Late Cretaceous respectively. The Eocene speciesKnightia bohaiensis was described in 1985 from theBohai Bay Basin region,[6] while"Knightia" yuyanga was first identified as Eocene when described from the Itu region in 1963.[7] The age of"K." yuyanga has been revised with the placement of the species'type locality in the Late CretaceousPaomagang Formation.[8] Additionally the species placement inKnightia has been questioned, and the species is now treated as "Clupeidincertae sedis".[9]
The Cretaceous genusEllimma from Brazil was formerly synonymized intoKnightia asKnightia branneri by Schaeffer (1947). This placement was rejected by Grande (1982) and subsequent authors, and the species moved back toEllimma branneri.[10]
InKnightia fish, rows ofdorsal andventralscutes 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.[11]K. alta was shorter and relatively wider, with specimens averaging between 6 and 10 cm.[11]
A smallschooling fish,Knightia made an abundant food source for larger Eocene predators. TheGreen River Formation has yielded many fossils of larger fish species preying onKnightia; specimens ofDiplomystus,Lepisosteus,Amphiplaga,Mioplosus,Phareodus,Amia, andAstephus have all been found withKnightia in either their jaws or stomachs.[4]
