End-Botomian mass extinction

Botomian
Marine extinction intensity during Phanerozoic
%
Millions of years ago
Apparent extinction intensity, i.e. the fraction of genera going extinct at any given time, as reconstructed from the fossil record. (Graph not meant to include recent epoch of Holocene extinction event)

The end-Botomian mass extinction event, also known as the late early Cambrian extinctions, refer to two extinction intervals that occurred during Stages 4 and 5 of the Cambrian Period, approximately 513 to 509 million years ago. Estimates for the decline in global diversity over these events range from 50% of marine genera up to 80%. Among the organisms affected by this event were the small shelly fossils, archaeocyathids (an extinct group of sponges), trilobites, brachiopods, hyoliths, and mollusks.

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