The sea fills with reefs
Marine diversity triples and the first coral reefs are built
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The Great Ordovician Biodiversification Event raised the number of marine genera more sharply than the Cambrian explosion did, but without creating new body plans — it filled out the ones that already existed. Stromatoporoids and tabulate and rugose corals built the first genuinely large reefs. The causes debated include cooling, increased nutrient flux from weathering, and Gondwana lying such that shallow seas were unusually extensive. Reefs would be destroyed and rebuilt at least five times since.
For children
After the Cambrian explosion came an even bigger flowering. The number of species in the sea tripled, and for the first time animals built large reefs of limestone. Reefs are the most species-rich places in the ocean — rainforests underwater.
Connects to
Part of Terra Saga — the story of Earth on a timeline. terrasaga.org