''Bajaichthys elegans'' is an extinct

Lutetian The Lutetian is, in the geologic timescale, a stage or age in the Eocene. It spans the time between . The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it is sometimes referred to as the ...

(middle

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

) zeid from the Monte Bolca Lagerstätten.

Anatomy and appearance

The holotype is four centimeters in length. It has a deep, oblong-shaped body, a deep, but short head, a long tail composed of 27 caudal

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristi ...

e, a long, crest-like dorsal fin, a long, banner-like anal fin with 29 to 30 rays running from the posterior region of the body down the entire length of the tail, and two enormous, wing-like pelvic fins. The holotype (and only known specimen) was originally described as the remains of a larval ("youthful") form due to its small size and due to its strong similarity to the larval form of trachypterid

ribbonfish The ribbonfish are any lampriform fishes in the family Trachipteridae. These pelagic fish are named for their slim, ribbon-like appearance. They are rarely seen alive, as they typically live in deep waters, though are not bottom feeders. The p ...

Taxonomic status

''Bajaichthys elegans taxonomic has been debated since its description in 1983. Because it appeared to combine features of both taeniosomid lamprids (i.e., its larval form resembles those of

oarfish Oarfish are huge, greatly elongated, pelagic lampriform fish belonging to the small family Regalecidae. Found in areas spanning from temperate ocean zones to tropical ones, yet rarely seen, the oarfish family contains three species in two gene ...

and

), and of ''

Bathysoma ''Bathysoma lutkeni'' is an extinct lamprid from the Danian age of Sweden, and is the second oldest lamprid known, after ''Nardovelifer'' of Campanian/Maastrichtian Italy. ''B. lutkeni'' has a disk-shaped body and an elongated head. It was ori ...

'' lamprids (the anatomy of the pelvis is extremely similar to that of sailfins), it was attributed to an ''incertae sedis'' position within

Lampriformes Lampriformes is an order of ray-finned fish. Members are collectively called lamprids (which is more properly used for the Lampridae) or lampriforms, and unite such open-ocean and partially deep-sea Teleostei as the crestfishes, oarfish, opah ...

. Further research placed it within

Zeiformes The Zeiformes are a small order of marine ray-finned fishes most notable for the dories, a group of common food fish. The order consists of about 33 species in seven families, mostly deep-sea types. Zeiform bodies are usually thin and deep. Mo ...

, another group of

acanthomorph Acanthomorpha (meaning "thorn-shaped") is an extraordinarily diverse taxon of teleost fishes with spiny rays. The clade contains about one third of the world's modern species of vertebrates: over 14,000 species. A key anatomical innovation in ...

teleosts Teleostei (; Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts ), is, by far, the largest infraclass in the class Actinopterygii, the ray-finned fishes, containing 96% of all extant species of fish. Teleo ...

References

External links

''Bajaicthys''
at the

Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database (PBDB) originated in the NCEAS-funded Phanerozoic Marine Pale ...

Zeiformes Eocene fish Fossils of Italy Fossil taxa described in 1983 {{Zeiformes-stub