When do the first arthropod fossils appear in the geologic record?

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A spiny lobster (Palinurus elephas) with long, striped antennae and spiny body stands on sandy ground near a rocky crevice underwater. — arthropod Spiny lobster, or rock lobster (*Palinurus elephas*).

The first fossil arthropods appear in the Cambrian Period, which occurred approximately 541.0 million to 485.4 million years ago.1

These early representatives of the phylum Arthropoda include trilobites, merostomes, and crustaceans, as well as various enigmatic forms that do not align with existing subphyla. The fossil record of this period is particularly enriched by rare deposits of soft-bodied organisms, such as the Burgess Shale in Canada and the Chengjian Biota in China, which provide remarkable detail regarding the diversity and ecology of these early arthropod communities.12