Trilobita (jan 1, 522000000 BC – jan 1, 251900000 BC)

Description:

Trilobites are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period, with trilobites reaching an apex of diversity during the late Cambrian-Ordovician, and remained diverse during the following Silurian and early Devonian. During the mid-late Devonian, their diversity strongly declined, being impacted by the successive Taghanic, Kellwasser and Hangenberg extinction events, wiping out most trilobite diversity and leaving Proetida as the only surviving order. Trilobite diversity never recovered to its former levels, remaining persistently low during the following Carboniferous and Permian periods. The last trilobites disappeared in the end-Permian mass extinction event about 251.9 million years ago, by which time only a handful of species remained. Trilobites were among the most successful of all early animals, existing in oceans for almost 270 million years, with over 22,000 species having been described.

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