Trilobite Triarthrus becki ventral view

Trilobites belong to the group of arthropods, animals with segmented bodies and jointed limbs, which lived for about 300 million years in the ancient oceans. The carapace was made of calcium carbonate which gave it rigidity and favored fossilization. There are about 20,000 described species, presenting great diversity of shape and size and corresponding to one of the most diverse groups of extinct animals. The abundance of Trilobites in the fossil record is due to the occurrence of growing seedlings. The flexibility of the thoracic segments allows the coiling of trilobites. They had compound eyes, that is, multiple individual eyes, very sensitive to movement and light variations. Before the emergence of dinosaurs, trilobites ruled the planet.