Ordovician radiation

The Ordovician radiation was the diversification of animal life at the start of the Ordovician period, just 40 million years after the Cambrian explosion.It followed a series of extinction events at the Cambrian-Ordovician boundary, and the resulting fauna went on to dominate the Palaeozoic relatively unchanged..Marine diversity to levels typical of the Palaeozoic,cite journal
author = Marshall, C.
year = 2006
title = Explaining the Cambrian "Explosion" of Animals
journal = Annual Review of Earth and Planetary Sciences
volume = 34
pages = 355–384
doi = 10.1146/annurev.earth.33.031504.103001
url = http://arjournals.annualreviews.org/doi/full/10.1146/annurev.earth.33.031504.103001
] and disparity was similar to today's.cite journal
author = Bush, A.M.; Bambach, R.K.; Daley, G.M
year = 2007
title = Changes in Theoretical Ecospace Utilization in Marine Fossil Assemblages Between the Mid-Paleozoic and Late Cenozoic
journal = Paleobiology
volume = 33
issue = 1
pages = 76–97
doi = 10.1666/06013.1
url = http://www.bioone.org/perlserv/?request=get-abstract
] cite journal
author = Bambach, R.K.; Bush, A.M.; Erwin, D.H
year = 2007
title = Autecology and the Filling of Ecospace: Key Metazoan Radiations
journal = Palaeontology
volume = 50
pages = 1
doi = 10.1111/j.1475-4983.2006.00611.x
] The diversity increase was neither global nor instantaneous; it happened at different times in different places.


The causes of the explosion are complex, and probably varied for different localities. Possible causes include changes in palaeogeography or tectonic activity, as well as a modified nutrient supply.cite journal
author = Botting, Muir
year = 2008
title = Unravelling Causal Components of the Ordovician Radiation: the Builth Inlier (Central Wales) As a Case Study
journal = Lethaia
volume = 41
pages = 111
doi = 10.1111/j.1502-3931.2008.00118.x

The above triggers would have been amplified by ecological escalation, whereby any new species would co-evolve with others, creating new niches through niche partitioning, tropic layering, or by providing a new habitat.clarifyme


The only phylum not to be represented in the Cambrian period, the Bryozoa, is first observed after this Ordovician radiation. Diversity increased manifold; the total number of marine orders doubled, and families tripled.cite journal
author = Droser, Mary L.; Finnegan, Seth
year = 2003
title = The Ordovician Radiation: A Follow-up to the Cambrian Explosion?
journal = Integrative and Comparative Biology
volume = 43
issue = 1
pages = 178
doi = 10.1093/icb/43.1.178

The acritarch record displays the Ordovician radiation beautifully; both diversity and disparity peaked in the middle Ordovician.cite journal
author = Servais, T.; Lehnert, O.; Li, Jun; Mullins, G.L
year = 2008
title = The Ordovician Biodiversification: Revolution in the Oceanic Trophic Chain
journal = Lethaia
volume = 41
pages = 99
doi = 10.1111/j.1502-3931.2008.00115.x
] The warm waters and high sea level (this had been rising steadily since the early Cambrian) permitted large numbers of phytoplankton to prosper; the accompanying diversification of the phytoplankton may have caused an accompanying radiation of zooplankton and suspension feeders.

ee also

Cambrian explosion


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  • Ordovician Period — Interval of geologic time, 490–443 million years ago, the second oldest period of the Paleozoic Era. It follows the Cambrian and precedes the Silurian. During the Ordovician, many of the landmasses were aligned in the tropics. Life was dominated… …   Universalium

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