Britannica Sources used in this answer

How did adaptive radiation follow Cambrian extinction events?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Cambrian paleogeography — Cambrian Period Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the late Cambrian Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.

During the Cambrian Period, extinction events—specifically those known as biomere events—frequently disrupted marine ecosystems, particularly affecting low-latitude shelf communities. These events were likely triggered by abrupt drops in water temperature, which proved fatal to the larvae of many marine invertebrates.1

Following each of these extinction events, the affected shelf environments were repopulated by trilobite faunas that were relatively simple in form and low in diversity. These repopulating organisms apparently emigrated from deeper, cooler off-shelf environments. This process of recovery was consistently followed by an adaptive radiation of new taxa, particularly among the trilobites, as they diversified to fill the ecological niches left vacant by the extinction.1

While these specific biomere events caused significant turnover, the broader Cambrian Period was also characterized by a more general, massive adaptive radiation known as the Cambrian explosion, which saw the appearance of most major animal phyla.23