Lycoptera is an extinct genus of fish that lived from Lower Cretaceous, Barremian to Aptian in present-day China, North Korea, Mongolia and Siberia. Although there is record from Jurassic Formation in Siberia, its age remains questionable. It is known from abundant fossils representing sixteen species, which serve as important index fossil used to date geologic formations in China. Along with the genus Peipiaosteus, Lycoptera has been considered a defining member of the Jehol Biota, a prehistoric ecosystem famous for its feathered dinosaurs, which flourished for 20 million years during the Early Cretaceous, where it occurs abundantly in often monospecific beds, where they are thought to have died in seasonal mass death events.Jin, F., Zhang, F.C., Li, Z.H., Zhang, J.Y., Li, C. and Zhou, Z.H. (2008). "On the horizon of Protopteryx and the early vertebrate fossil assemblages of the Jehol Biota." Chinese Science Bulletin, 53(18): 2820-2827. Lycoptera is a crown group teleost belonging to an early diverging lineage of the Osteoglossomorpha, which contains living mooneyes, arapaima, arowana, elephantfish and knifefish/featherbacks.
Description and ecology
Lycoptera was a small freshwater fish. Most species fed on plankton, and had numerous tiny teeth. A few species like L. gansuensis, L. muroii, and L. sinensis had larger teeth and probably fed on small insects and their larvae.
Many specimens preserve minute details and impressions of soft tissues, and fossils are often orange in color. Lycoptera was covered in tiny oval scales about 1.2 millimeters across, and, in life, would have had a superficial resemblance to the common minnow.
Lycoptera fossils are commonly found in large groups, buried together quickly in fine lake sediments likely due to mass death events from seasonal upwelling of anoxic waters during late autumn and winter. This has led to suggestions that they were gregarious in life, congregating in shoals.
Lycoptera was preyed on by other fish within the Jehol Biota lake ecosystems, such as the primitive paddlefish Protopsephurus and the peipaiosteid (an extinct relative of sturgeons and paddlefish) Yanosteus, which have been found with Lycoptera remains as stomach contents. The long-necked choristodere reptile Hyphalosaurus has also been proposed as a likely predator.
Classification and species
Sixteen species of Lycoptera have been described, nine from the Jehol Group. The table below is based primarily on the valid species listed by Zhang and Jin in the 2008 book The Jehol Fossils.
Name Author Year Status NotesLycoptera middendorffiMüller1847Valid, type speciesLycoptera macrorhyncha(Eichwald)(1868)Lycoptera davidi(Sauvage)(1880)ValidLycoptera sinensisWoodward1901ValidLycoptera feroxGrabau1923Lycoptera chosenensisMakiyama1927Lycoptera kansuensisGrabau1928Lycoptera woodwardiGrabau1928Lycoptera jaholensisGrabau1928Lycoptera fragilisHussakof1932ValidLycoptera takunagaiSeito1936ValidLycoptera muroii(Takai)(1943)ValidLycoptera longicephalusLiu et al.1962ValidLycoptera lunteensisLiu et al.1962Lycoptera polyspondylusLiu et al.1962Lycoptera tungiLiu et al.1962Lycoptera wangiLycoptera sankeyushuensis(Ma & Sun)(1988)ValidLycoptera fuxinensisZhang2002Valid
References