Evolution of fish

origin and diversification of fish through geologic time

The evolution of fish began about 530 million years ago during the Cambrian explosion. One of the earliest jawless fish include Haikouichthys, a craniate. The conodonts were another Agnatha. The earliest jawed vertebrates developed during the late Ordovician period.

Devonian fish

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 change

The mouth of a lamprey

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.

Conodonts change

The conodonts are an extinct group of agnathans that looked like eels. They appeared 520 ma and died 200 ma. One of them is Promissum.

Chondrichthyes change

Main article: Chondrichthyes

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

Extinct cartilaginous fishes change

Living fossils change


Main article: Living fossil

Bony fish change

Actinopterygii change

Main article: Actinopterygii


Actinopterygii is the class of ray-finned fish. Actinopterygians are the largest class of vertebrates.

Sarcopterygii change

Main article: 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 change

Placodermi change

Main article: Placoderm

The placoderms were a class of armoured prehistoric fish.

Dunkleosteus change

Main article: Dunkleosteus


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

Materpiscis change

Main article: Materpiscis

Materpiscis was a ptyctodontid fish from the Late Devonian.

Related pages change

References change

  1. Lecointre, G; Le Guyader, H (2007). The Tree of Life: A Phylogenetic Classification. Harvard University Press Reference Library.
  2. Haines, Tim; Chambers, Paul (2005). The Complete Guide to Prehistoric Life. Firefly Books.

Other websites change