Knightia

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Knightia
Temporal range: Early Eocene
Knightia eocaena Green River Formation, Wyoming 2.jpg
Knightia eocaena specimen
Scientific classification OOjs UI icon edit-ltr.svg
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
  • K. alta(Leidy, 1873)
  • K. bohaiensisZhang, Zhou & Qing, 1985
  • K. eocaena Jordan 1907
  • K. vetustaGrande, 1982
  • ?K. yuyangaLiu, 1963
Synonyms
  • Clupea alta(Leidy, 1873)
  • Clupea eocaenaJordan, 1907
  • Clupea humulusLeidy, 1856
  • Clupea pusillaCope, 1870
  • Knightia copeiTanner, 1925

Knightia is an extinct genus of clupeid bony fish that lived in the freshwater lakes and rivers of North America and Asia during the Eocene epoch. The genus was erected by David Starr Jordan in 1907, in honor of the late University of Wyoming professor Wilbur Clinton Knight, "an indefatigable student of the paleontology of the Rocky Mountains." [1] It is the official state fossil of Wyoming, [2] and the most commonly excavated fossil fish in the world. [3]

Contents

Taxonomy

Knightia belongs to the same taxonomic family as herring and sardines, 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 .

As with modern-day clupeids, Knightia spp. likely fed on algae and diatoms, as well as insects and occasionally smaller fish. [4] In a 2022 paper, researchers announced they had detected biological residues in Knightia fossils from the Green 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 species Knightia bohaiensis was described in 1985 from the Bohai 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 Cretaceous Paomagang Formation. [8] Additionally the species placement in Knightia has been questioned, and the species is now treated as "Clupeid incertae sedis". [9]

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 . [10]

Anatomy

In Knightia fish, rows of dorsal and ventral scutes 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]

Predators

A small schooling fish, Knightia made an abundant food source for larger Eocene predators. The Green River Formation has yielded many fossils of larger fish species preying on Knightia; specimens of Diplomystus , Lepisosteus , Amphiplaga , Mioplosus , Phareodus , Amia , and Astephus have all been found with Knightia in either their jaws or stomachs. [4]

Knightia eocaena FBNM.JPG
Slab of fossilized Knightia eocaena from Fossil Butte National Monument
Knightia BW.jpg
Digital artist's conception of Knightia sp.
17 22 008 fossil.jpg
Knightia fossils from Green River Formation of Wyoming

Related Research Articles

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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 in Colorado, Wyoming, and Utah. The sediments are deposited in very fine layers, a dark layer during the growing season and a light-hue inorganic layer in the dry season. Each pair of layers is called a varve and represents one year. The sediments of the Green River Formation present a continuous record of six million years. The mean thickness of a varve here is 0.18 mm, with a minimum thickness of 0.014 mm and maximum of 9.8 mm.

<span class="mw-page-title-main">Fossil Butte National Monument</span> National monument in the United States

Fossil Butte National Monument is a United States National Monument managed by the National Park Service, located 15 miles (24 km) west of Kemmerer, Wyoming, United States. It centers on an assemblage of Eocene Epoch animal and plant fossils associated with Fossil Lake—the smallest lake of the three great lakes which were then present in what are now Wyoming, Utah, and Colorado. The other two lakes were Lake Gosiute and Lake Uinta. Fossil Butte National Monument was established as a national monument on October 23, 1972.

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<i>Diplomystus</i> Extinct genus of fishes

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<i>Gasteroclupea</i> Extinct genus of fishes

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<i>Priscacara</i> Extinct genus of fishes

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<i>Araripichthys</i> Extinct genus of ray-finned fishes

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References

  1. ↑ Jordan, D. S. 1907. "The fossil fishes of California; with supplementary notes on other species of extinct fishes". Bulletin Department of Geology, University of California 5:136
  2. ↑ "Wyoming Secretary of State". Archived from the original on 2011-09-06. Retrieved 2011-01-22.
  3. ↑ Kelley, Patricia H.; Kowalewski, Michał; Hansen, Thor A. (2003). Predator-prey interactions in the fossil record. Springer. ISBN   0-306-47489-1.
  4. 1 2 Grande, L. 1980. The paleontology of the Green River Formation, with a review of the fish fauna. Wyoming Geol. Surv., Bull. 63, pp. 85.
  5. ↑ Misra, Anupam K.; Rowley, Sonia J.; Zhou, Jie; Acosta-Maeda, Tayro E.; Dasilveira, Luis; Ravizza, Gregory; Ohtaki, Kenta; Weatherby, Tina M.; Trimble, A. Zachary; Boll, Patrick; Porter, John N.; McKay, Christopher P. (2022-06-17). "Biofinder detects biological remains in Green River fish fossils from Eocene epoch at video speed". Scientific Reports. 12 (1): 10164. Bibcode:2022NatSR..1210164M. doi:10.1038/s41598-022-14410-8. ISSN   2045-2322. PMC   9205911 . PMID   35715549.
  6. ↑ Zhang, M.M.; Zhou, J.J.; Qin, D.R. (1985). "Tertiary fish fauna from coastal region of Bohai Sea". Academia Sinica Institute of Vertebrate Paleontology and Paleoanthropology Memoirs. 17: 1–60.
  7. ↑ Liu, H. (1963). "The discovery of double-armoured herrings from Itu, Hupei". Vertebrata PalAsiatica. 7 (1): 31–37.
  8. ↑ Wang, P.; Zheng, H.; Liu, S.; Hoke, G. (2018). "Late Cretaceous drainage reorganization of the middle Yangtze River". Lithosphere. 10 (3): 392–405. Bibcode:2018Lsphe..10..392W. doi:10.1130/L695.1.
  9. ↑ Lavoue, S.; Miya, M.; Musikasinthorn, P.; Chen, W.J.; Nishida, M. (2013). "Mitogenomic evidence for an Indo-west Pacific origin of the Clupeoidei (Teleostei: Clupeiformes)". PLOS ONE. 8 (2): e56485. Bibcode:2013PLoSO...856485L. doi: 10.1371/journal.pone.0056485 . PMID   23431379.
  10. ↑ Chang, M.; Maisey, J. (2003). "Redescription of †Ellimma branneri and †Diplomystus shengliensis, and Relationships of Some Basal Clupeomorphs". American Museum Novitates (3404): 1–35. doi:10.1206/0003-0082(2003)404<0001:ROEBAD>2.0.CO;2. hdl:2246/2830.
  11. 1 2 Grande, Lance (June 7, 1982). "A Revision of the Fossil Genus †Knightia, With a Description of a New Genus From the Green River Formation (Teleostei, Clupeidae)" (PDF). American Museum Novitates. ISSN   0003-0082. OCLC   47720325. Archived from the original (PDF) on October 20, 2013. Retrieved November 12, 2011.
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