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What was the Ordovician radiation?
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Ordovician Period
The distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the Ordovician Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.
The Ordovician radiation was a significant interval of intense diversification of marine animal life that occurred during the Ordovician Period (approximately 486.9 million to 443.1 million years ago).1
Building upon the Cambrian explosion, this event saw a fourfold increase in the number of marine genera and the emergence of organisms that would dominate marine ecosystems for the remainder of the Paleozoic Era. Key developments included:1
- Ecological Complexity: Life expanded into new habitats, such as reefs and crinoid gardens, and established complex, multi-tiered communities that extended above the seafloor.12
- Taxonomic Shifts: While Cambrian-dominant groups like trilobites declined in shallow waters, other invertebrates—including brachiopods, bryozoans, mollusks, and corals—proliferated.13
- Drivers of Change: The exact causes remain unclear, though theories suggest that increased orogenic and volcanic activity may have fueled diversification by increasing nutrient supplies, alongside factors like biological interactions and increased provinciality between continents.14