Description

Trilobites are a group of 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, and they flourished throughout the lower Paleozoic before slipping into a long decline, when, during the Devonian, all trilobite orders except the Proetida died out. The last extant trilobites finally disappeared in the mass extinction at the end of the Permian about 252 million years ago. Trilobites were among the most successful of all early animals, existing in oceans for almost 270 million years, with over 20,000 species having been described.
Most trilobites are one of the first animals known to have the sense of vision. They had compound eyes contained lenses made of calcite crystals, something unique to trilobites. Trilobites had elaborate survival features such as eye stalks, spines, and an ability to enroll itself and shield its vulnerable parts from exposure. Most trilobites are one of the first animals known to have the sense of vision. They had compound eyes contained lenses made of calcite crystals, something unique to trilobites. Trilobites had elaborate survival features such as eye stalks, spines, and an ability to enroll itself and shield its vulnerable parts from exposure.