Trilobite

Trilobites were extinct marine arthropods in the class Trilobita, known for their three-lobed bodies and abundant fossil record.

Trilobites were extinct marine arthropods in the class Trilobita, known for their three-lobed bodies and abundant fossil record. They first appeared in the Cambrian Period, lived for nearly 270 million years, and went extinct at the end of the Permian Period. Thousands of species have been described, making them one of the best-known fossil groups.

Classification and body plan

Trilobites belong to the class Trilobita within the phylum Arthropoda. Their bodies are segmented and divided into three longitudinal lobes. The exoskeleton is commonly divided into three main regions: the cephalon (head), thorax, and pygidium (tail).

Evolution and fossil record

Trilobites first appeared in the early Cambrian Period, approximately 521 million years ago. They survived through most of the Paleozoic Era, going extinct at the end of the Permian Period around 251–252 million years ago. Their fossils are widespread and abundant, making them important index fossils for dating rock layers and studying ancient marine life.

Ecology and lifestyle

Trilobites were exclusively marine, inhabiting salt-water environments. They displayed a range of lifestyles: some crawled on the seafloor, others burrowed in sediment, and some swam in open water. They were especially diverse and abundant in Cambrian seas.

Extinction

Trilobites declined in diversity over the course of the Paleozoic. They became extinct at the end of the Permian Period, during the end-Permian mass extinction event, approximately 251–252 million years ago.