''Oreochima ellioti'' is an
archaeomaenid
Archaeomaenidae is an extinct family of stem- teleost fish found in freshwater environments of Jurassic New South Wales of Australia, China, and Antarctica, and in Lower Cretaceous New South Wales and Mongolia.
Archaeomaenidae was originally ere ...
ray-finned fish
Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species.
The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...
from
Lower Jurassic-aged freshwater strata of
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...
.
Fossils come from the Lower Jurassic
Carapace Formation (
Pliensbachian-
Toarcian
The Toarcian is, in the ICS' geologic timescale, an age and stage in the Early or Lower Jurassic. It spans the time between 182.7 Ma (million years ago) and 174.1 Ma. It follows the Pliensbachian and is followed by the Aalenian.
The Toarcian ...
) of
Storm Peak
Storm Peak () is a flat-topped peak, 3,280 m, standing 3.5 nautical miles (6 km) north of Blizzard Peak in the Marshall Mountains, Queen Alexandra Range. So named by the New Zealand Geological Survey Antarctic Expedition (NZGSAE) (1961–62) b ...
, Antarctica, where a freshwater lake system once existed.
[Schaeffer, Bobb]
"A Jurassic Fish from Antarctica"
American Museum of Natural History, 1972. ''O. ellioti'' is also notable for being one of three archaeomaenid genera found outside of
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
.
Description
Two nearly complete specimens of ''Oreochima ellioti'' (specimens AMNH 9910 and AMNH 9916) have an average total length of about 60 mm, with incomplete specimens represent individuals of similar size.
The frontals taper anteriorly and were slightly notched where they were in contact with the nasals. The opercular bone was about twice as high as the subopercular.
Paleoenvironment
The interbeds of the
Kirkpatrick Basalt record sedimentary and biotic processes in relatively shallow lakes and ponds, and in surrounding wetlands to upland areas, with the biota of the lakes having access to magmatic sources.
Hydrothermal activity help the development of microbes (
Archaea
Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...
) and helping the fauna on cooler events. Alongside ''Oreochima'' lived the
spinicaudatan ''
Carapacestheria disgregaris'',
notostracan branchiopods,
ostracoda
Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typical ...
,
insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...
nymphs and wings (
mayflies
Mayflies (also known as shadflies or fishflies in Canada and the upper Midwestern United States, as Canadian soldiers in the American Great Lakes region, and as up-winged flies in the United Kingdom) are aquatic insects belonging to the orde ...
, the
stonefly
Plecoptera is an order of insects, commonly known as stoneflies. Some 3,500 species are described worldwide, with new species still being discovered. Stoneflies are found worldwide, except Antarctica. Stoneflies are believed to be one of the mo ...
nymph ''
Uralonympha sehopfi'' and the
dragonfly
A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of true dragonfly are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threate ...
''
Caraphlebia antartica'', and a
Coleoptera
Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...
n), and plant leaves (''
Zamites
''Zamites'' is a genus of fossil tree known from the Mesozoic of North America, Europe and India through the Eocene of North America. It was erected as a form taxon for leaves that superficially resembled the extant cycad ''Zamia'', however it is ...
'').
[Stigall, A. L., Babcock, L. E., Briggs, D. E. G., & Leslie, S. A. (2008). Taphonomy of Lacustrine Interbeds in the Kirkpatrick Basalt (Jurassic), Antarctica. PALAIOS, 23(6), 344–355. .]
See also
*
List of prehistoric bony fish genera
This list of prehistoric bony fish is an attempt to create a comprehensive listing of all genera from the fossil record that have ever been considered to be bony fish (class Osteichthyes), excluding purely vernacular terms. The list includes al ...
References
External links
*
Early Jurassic fish
Fossil taxa described in 1972
Fossils of Antarctica
Prehistoric fish of Antarctica
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