Australosomus Explained

Australosomus (meaning "southern body") is an extinct genus of prehistoric ray-finned fish that lived during the Early Triassic epoch in what is now Greenland, Kenya, Tanzania, Madagascar, South Africa and Canada (British Columbia).^{[1] [2] [3]}

The type species, Australosomus merlei from Madagascar, was first described as Pristisomus merlei by Ferdinand Priem. A new genus, Australosomus, was later erected for this species by Jean Piveteau.^[4]

Australosomus is one of many genera to arise after the Permian-Triassic extinction event, only to die out during the Early Triassic,^[2] possibly during a subsequent extinction event.^[1]

Most species were marine, except for the African species, which were found in freshwater deposits.

The genus name Australosomus ("southern body") is inaccurate, as Australosomus is known as far north as Canada and Greenland, although the first known remains were described from Madagascar.

Taxonomy

Australosomus contains the following species:^[5]

• A. altisquamosus Beltan, 1980 - Late Induan of Madagascar (Sakamena Group)
• A. kochi Stensiö, 1932 - Early Induan (and possibly latest Permian) of Greenland (Wordie Creek Formation) (=A. simplex Nielsen, 1949)
• A. longirostris Beltan 1968 - Late Induan of Madagascar (Sakamena Group)
• A. merlei (Priem, 1924) - Late Induan of Madagascar (Sakamena Group)
• A. pholidopleuroides Nielsen, 1949 - Early Induan of Greenland (Wordie Creek Formation)
• A. stockleyi Haughton, 1936 - Induan of Tanzania (Karoo Supergroup)^[6]

Indeterminate remains are known from the Sulphur Mountain Formation of British Columbia and Alberta (Canada).^[7] The remains of a potentially associated genus are known from the Late Triassic Chinle Formation of Arizona. Potential remains are known from the Permian-Triassic boundary of Kenya.^[8]

Appearance

Australosomus was an elongate fish. The interlocking scales (3 to 4 times long as wide), deeply forked caudal fin all help to distinguish this genus.^[9] It achieved standard lengths of about to .

See also

• Prehistoric fish
• List of prehistoric bony fish

Notes and References

1. Ludvigsen, Rolf & Beard, Graham. 1997. West Coast Fossils: A Guide to the Ancient Life of Vancouver Island. pg. 78-79
2. Romano . Carlo . Koot . Martha B. . Kogan . Ilja . Brayard . Arnaud . Minikh . Alla V. . Brinkmann . Winand . Bucher . Hugo . Kriwet . Jürgen . Permian-Triassic Osteichthyes (bony fishes): diversity dynamics and body size evolution . Biological Reviews . 2016 . 91 . 1 . 106–147 . 10.1111/brv.12161 . 25431138 . 5332637.
3. Sepkoski . Jack . A compendium of fossil marine animal genera . Bulletins of American Paleontology . 364 . 560 . 2002 . 2009-02-27 . dead . https://web.archive.org/web/20110723131237/http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=611&rank=class . 2011-07-23 .
4. Piveteau . Jean . Jean Piveteau . 1930 . Particularités structurales d'un type nouveau de poisson fossile des formations permo-triasiques du nord de Madagascar . Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences . 191 . 456–458 . fr.
5. Web site: PBDB Taxon . 2024-05-08 . paleobiodb.org.
6. Murray . A.M. . 2000 . The Palaeozoic, Mesozoic and Early Cenozoic fishes of Africa . Fish and Fisheries . en . 1 . 2 . 111–145 . 10.1046/j.1467-2979.2000.00015.x . 1467-2960.
7. Neuman . Andrew G. . 2015 . Therrien . François . Fishes from the Lower Triassic portion of the Sulphur Mountain Formation in Alberta, Canada: geological context and taxonomic composition . Canadian Journal of Earth Sciences . en . 52 . 8 . 557–568 . 10.1139/cjes-2014-0165 . 0008-4077.
8. Hankel . O. . 1992-05-22 . Late Permian to early triassic microfloral assemblages from the Maji ya chumvi formation, Kenya . Review of Palaeobotany and Palynology . 72 . 1 . 129–147 . 10.1016/0034-6667(92)90181-F . 0034-6667.
9. Nielsen . Eigil . Eigil Nielsen (paleontologist) . 1949 . Studies on Triassic fishes from East Greenland 2. Australosomus and Birgeria . Palaeozoologica Groenlandica . 3 . 1–309.