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Which major groups of marine animals diversified during 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 period of intense diversification that significantly expanded marine biodiversity following the Cambrian explosion. During this interval, a wide array of marine invertebrates emerged and flourished, eventually dominating ecosystems for the remainder of the Paleozoic Era.1
Key groups that diversified during this time include:
- Brachiopods: Articulate (jointed) forms became particularly prominent, spreading into various habitats.12
- Mollusks: This group saw significant diversification, including gastropods, bivalves, and cephalopods.13
- Echinoderms: This phylum reached a peak diversity of 20 classes, with crinoids being especially common.3
- Corals: Both tabulata and rugosa (horn corals) made their first appearance.3
- Bryozoans: These "moss animals" emerged during the Ordovician and became a dominant component of many marine assemblages.13
- Other Invertebrates: Graptolites, conodonts, and various sponges—including the first stromatoporoids—also diversified significantly.13
While trilobites remained present, they were gradually replaced as the dominant group by these newer, more diverse invertebrate communities.13