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 ventralscutes 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]
Knightia fossils from Green River Formation of Wyoming
References
^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
^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.
^Liu, H. (1963). "The discovery of double-armoured herrings from Itu, Hupei". Vertebrata PalAsiatica. 7 (1): 31–37.
^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.
