Trilobites are a class of extinct arthropods. They are the most characteristic fossils of the Paleozoic Era. They appeared in the Cambrian period (at the beginning of the Paleozoic, about 540 million years ago).
The trilobites have a flattened and smooth body, oval and divided into three tagmas, cephalon, thorax and pigidium. They have two longitudinal grooves that divide the body into three clearly defined lobes (from which its name derives).
Dinosaurs lived in the Mezosoic era that began 251 million years ago.
