Evolution of fish

The evolution of fish began about 530 million years ago during the Cambrian explosion. One of the earliest jawless fish evolved, including Haikouichthys, who dates back from the Middle Cambrian. The conodonts were another Agnatha. The earliest jawed vertebrates developed during the late Ordovician period.

During the Devonian period, a great increase in fish variety occurred, especially among the ostracoderms and placoderms, and also among the lobe-finned fish and early sharks, which meant that this was the age of fishes.

Agnatha

The Agnatha (meaning "no jaws") is a superclass of fish in the phylum Chordata, subphylum Vertebrata. Agnatha comes from the Greek. The first armoured agnathans were the ostracoderms, precursors to the bony fish and hence to the tetrapods.

Panderodus

Conodonts

The conodonts are an extinct group of agnathans that looked like eels. They appeared in a different time and died out 200 million years ago. One of them is a creature called Promissum.

Life restoration of *Promissum pulchurum*

Chondrichthyes

The Chondrichthyes, consisting of sharks, rays and chimaeras, appeared by about 395 million years ago, in the middle Devonian.

Extinct cartilaginous fishes

Helicoprion - a fish famous for its tooth whorls.
Goodrichthys - another genus of fish.
Megalodon - the largest Cenozoic predator ever to exist on Earth.

Living fossils

Bony fish

Further information: Osteichthyes and List of prehistoric bony fish genera

The bony fish, Osteichthyes, have skeletons primarily made of bone.^[1] It is divided into two groups, the Actinopterygii and Sarcopterygii.

The earliest known fossils of bony fish, such as Eosteus, are about 436 million years old from the early Silurian period.^[2] Another early bony fish is Andreolepis, which lived around 420 million years ago.^[3]

Actinopterygii

Actinopterygii is the class of ray-finned fish. Actinopterygians are the largest class of vertebrates. The vast majority are teleosts.^[4]

Actinopterygii differ from the lobe-finned fish in that their fins are supported by spines. Ray-finned fish normally have skeletons made from bone, but it is not true for sturgeons and paddlefish.^[5]

The earliest definitive actinopterygian is likely Meemannia eos, which was once considered a lobe-finned fish.^[6] Alternatively, Cheirolepis can be considered.^[6]

Sarcopterygii

Lobe-finned fishes, class Sarcopterygii, are mostly extinct bony fishes. They lived a very long time ago. Most of them died already, while few, such as the coelacanths, have survived.

The first tetrapodomorphs, which included the rhizodonts, had the same general anatomy as the lungfish, who were their closest kin, but they appear not to have left their water habitat until the late Devonian epoch (385 - 359 Ma), with the first appearance of tetrapods.

Devonian fish

Placodermi

The placoderms were a class of armoured prehistoric fish.

Dunkleosteus

Dunkleosteus was a giant creature that lived during the Devonian period.

Materpiscis

Materpiscis was an organism from the Late Devonian.

Gallery

Evolution of Chondrichthyes, derived from work by Michael Benton, 2005^[7]
A West Indian Ocean coelacanth. Coelacanths are loosely called living fossils.
Meemannia
Waterloo Farm biota from South Africa. In the center is a fish known as Hyneria.^[8]
Evolution of ray finned fish

Related pages

References

↑ http://www.seaworld.org/animal-info/info-books/bony-fish/scientific-classification.htm
↑ "The oldest articulated bony fish from the early Silurian period". Nature. doi:10.1038/s41586-026-10125-2.
↑ Märss, T. (2001). "ANDREOLEPIS (ACTINOPTERYGII) IN THE UPPER SILURIAN OF NORTHERN EURASIA". Proceedings of the Estonian Academy of Sciences, Geology. 50 (3): 174–189. doi:10.3176/geol.2001.3.03.
↑ Fishes of the World, Joseph S. Nelson. ISBN 978-1-118-34233-6
↑ "Introduction to the Actinopterygii". Museum of Palaeontology, University of California.
1 2 Lu, Jing; Giles, Sam; den Blaauwen, Jan L.; Zhu, Min (2016). "The Oldest Actinopterygian Highlights the Cryptic Early History of the Hyperdiverse Ray-Finned Fishes". Current Biology. 26 (12): 1602–1608. doi:10.1016/j.cub.2016.04.045. PMID 27212403.
↑ Benton, Michael (2005) Vertebrate Palaeontology, Blackwell, 3rd edition, Fig 7.13 on page 185
↑ https://doi.org/10.1371/journal.pone.0281333.g013

Other websites

"Fish", British Geological Survey
Age of Fishes Museum

[1] ttp://www.seaworld.org/animal-info/info-books/bony-fish/scientific-classification.htm

[2] "The oldest articulated bony fish from the early Silurian period". Nature. doi:10.1038/s41586-026-10125-2.

[3] Märss, T. (2001). "ANDREOLEPIS (ACTINOPTERYGII) IN THE UPPER SILURIAN OF NORTHERN EURASIA". Proceedings of the Estonian Academy of Sciences, Geology. 50 (3): 174–189. doi:10.3176/geol.2001.3.03.

[4] Fishes of the World, Joseph S. Nelson. ISBN 978-1-118-34233-6

[5] "Introduction to the Actinopterygii". Museum of Palaeontology, University of California.

[:0-6] 1 2 Lu, Jing; Giles, Sam; den Blaauwen, Jan L.; Zhu, Min (2016). "The Oldest Actinopterygian Highlights the Cryptic Early History of the Hyperdiverse Ray-Finned Fishes". Current Biology. 26 (12): 1602–1608. doi:10.1016/j.cub.2016.04.045. PMID 27212403.

[7] Benton, Michael (2005) Vertebrate Palaeontology, Blackwell, 3rd edition, Fig 7.13 on page 185

[8] ttps://doi.org/10.1371/journal.pone.0281333.g013

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