Polymixia Explained

Polymixia is the only extant genus of the order Polymixiiformes and family Polymixiidae. It contains 10 species, all of which live in deepwater marine environments. They are found in tropical and subtropical waters of the Atlantic, Indian and western Pacific Oceans. They are bottom-dwelling fish, found down to about 800m (2,600feet). Most are relatively small fish, although one species is over 40cm (20inches) in length.^[1] They can be considered "living fossils" due to being the only surviving members of the once-diverse order Polymixiiformes.^[2]

Classification

There are currently 12 recognized species in this genus:

• Polymixia berndti C. H. Gilbert, 1905 (Pacific beardfish)
• Polymixia busakhini Kotlyar, 1993 (Busakhin's beardfish)
• Polymixia carmenae Caixeta, Oliveira & de Melo, 2024 (Brazilian beardfish)^[3]
• Polymixia fusca Kotthaus, 1970
• Polymixia hollisterae Grande & Wilson, 2021 (Bermuda beardfish)^[4]
• Polymixia japonica Günther, 1877 (Silver eye)
• Polymixia longispina S. M. Deng, G. Q. Xiong & H. X. Zhan, 1983
• Polymixia lowei Günther, 1859 (Beardfish)
• Polymixia nobilis R. T. Lowe, 1838 (Stout beardfish)
• Polymixia salagomeziensis Kotlyar, 1991
• Polymixia sazonovi Kotlyar, 1992
• Polymixia yuri Kotlyar, 1982

The extinct species Polymixia polita Schwarzhans, 2012 is known from fossil otoliths from the early and late Paleocene of Germany and Austria.^[5] Another otolith-based taxon that may possibly belong to this genus, Polymixia? harderi (Schwarzhans, 2003) is known from the late Maastrichtian and early Paleocene of Denmark, in addition to a potential earlier record from the Campanian of North Carolina, USA; this may suggest Late Cretaceous origins for the genus.^{[6] [7]}

Notes and References

1. Book: Paxton, J.R. . Eschmeyer, W.N. . Paxton, John R.. 1998. Encyclopedia of Fishes. Academic Press. San Diego. 161. 0-12-547665-5.
2. De Cia Caixeta . Heloísa . Oliveira . Claudio . Melo . Marcelo Roberto Souto de . 2024-03-01 . Another piece of the living fossil puzzle: A new species of Polymixia Lowe, 1836 (Polymixiiformes: Polymixiidae) from the western South Atlantic . Deep Sea Research Part I: Oceanographic Research Papers . 205 . 104249 . 10.1016/j.dsr.2024.104249 . 0967-0637.
3. De Cia Caixeta . Heloísa . Oliveira . Claudio . Melo . Marcelo Roberto Souto de . 2024-03-01 . Another piece of the living fossil puzzle: A new species of Polymixia Lowe, 1836 (Polymixiiformes: Polymixiidae) from the western South Atlantic . Deep Sea Research Part I: Oceanographic Research Papers . 205 . 104249 . 10.1016/j.dsr.2024.104249 . 0967-0637.
4. Grande . Terry C. . Wilson . Mark V. H. . 2021-07-16 . A New Cryptic Species of Polymixia (Teleostei, Acanthomorpha, Polymixiiformes, Polymixiidae) Revealed by Molecules and Morphology . Ichthyology & Herpetology . 109 . 2 . 10.1643/i2020112 . 2766-1512. free .
5. Schwarzhans . Werner . 2012 . Fish otoliths from the Paleocene of Bavaria (Kressenberg) and Austria (Kroisbach and Oiching-Graben) / / Werner Schwarzhans. . Palaeo Ichthyologica . 12 . 1-88 .
6. Web site: 2017-02-15 . Bulletin Volume 65 – 2017 . 2024-07-28 . Dansk Geologisk Forening . da-DK . 10.37570/bgsd-2017-65-05.
7. Stringer . Gary L. . Clements . Don . Sadorf . Eric . Shannon . Kevin . 2019 . First Description and Significance of Cretaceous Teleostean Otoliths (Tar Heel Formation, Campanian) from North Carolina . Eastern Paleontologist . 4 . 1–22 . 2475-5117.