Evolutionary fauna

The concept of the three great Evolutionary Faunas of marine animals from the Cambrian to the Present (that is, the entire Phanerozoic) was introduced by Jack Sepkoski in 1981 using factor analysis of the fossil record.

Cambrian fauna

Fauna I, known as "Cambrian", described as a "Trilobite-rich assemblage", encompasses the bulk of the fossils which first appeared in the Cambrian explosion, and largely went extinct in the Ordovician-Silurian extinction event, although the genus Lingula has survived to the present. This fauna is marked by fossils of the following classes: Trilobita, Polychaeta, Monoplacophora, Inarticulata.

Paleozoic fauna

Fauna II, known as "Paleozoic", described as a "Brachiopod-rich assemblage", accounts for most of the fossils appearing in the Great Ordovician Biodiversification Event, and largely went extinct in the Permian-Triassic extinction event. This fauna is marked by fossils of the following classes: Articulata, Crinoidea, Ostracoda, Cephalopoda, Anthozoa, Stenolaemata, Stelleroidea.

Modern fauna

Fauna III, known as "Modern", described as a Mollusc-rich assemblage", arose largely in the Mesozoic-Cenozoic Radiation, still in progress.The following classes are included: Gastropoda, Bivalvia, Osteichthyes, Malacostraca, Echinoidea, Gymnolaemata, Demospongiae, Chondrichthyes.

Further reading

• Anthony Hallam (1994). "4. Major temporal changes through the Phanerozoic". An Outline of Panerozoic Biogeography. Oxford Biogeography Series. Oxford: Oxford University Press. pp. 35–50. ISBN 0-19-854060-4.
• Arnold I. Miller (2002). "Diversity of Life Through Time". Encyclopedia of Life Sciences. John Wiley & Sons.
• The Succession of Life in the Sea