Why is the Cambrian Period sometimes called the Age of Trilobites?

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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.

The Cambrian Period is sometimes called the Age of Trilobites because of the exceptional adaptive radiation of trilobites that occurred following the appearance of their mineralized skeletons.1

These extinct arthropods evolved rapidly and became the dominant life form in the seas during this time. Their fossilized remains are so abundant that they dominate most later Cambrian deposits, making them the principal guide fossils used for biostratigraphic zonation throughout the period. Because of their rapid evolution and widespread presence, they are essential for understanding the geologic history of the Cambrian.1234