Trilobites belong to the artiopoda, a group of extinct arthropods morphologically similar to trilobites, though only the trilobites had heavily mineralised exoskeletons.. Trilobites are a group of extinct marine arthropods that first appeared around 521 million years ago, shortly after the beginning of the cambrian period, living through the majority of.
Trilobites rank among the most important early animals.. Our knowledge of them has been gained from the study of their fossils, usually the impressions left of their shells after burial in sediment that.