Trilobites

Trilobites are a group of small and medium-sized marine Arthropods that lived during the Paleozoic Era and disappeared completely at the end of the Permian (about 230 million years ago), albeit their mass extinction took place at the end of the Devonian.

Trilobites are found in marine deposits of various types of environments. This indicates how these animals adapted to the different environmental conditions. The flattened body, the position of the mouth and eyes (which are totally absent in some forms), the structure and appendage arrangement in any case show that most Trilobites were bentonic animals, which dug into the sediment, walked and swam on the sea bed.  To this purpose, the finding of fossil tracks (Cruzian) left by these Arthropods in fine sediments is significant.

Trilobites ate mud and microorganisms. Their growth would take place in moults, that were more or less frequent in the first stages of their growth. They were preys of fish and Cephalopods, that in this way contributed to their extinction.

The name comes from the esokeleton’s shape, from slightly convex to flat, which is divided into three parts both lengthwise and crosswise. Lengthwise, a central part (or rachis) can be observed as well as two lateral lobes called pleura. Crosswise, it is composed of a front part (or cephalon), middle (or thorax) and back part (or pygidium).

Trilobites are considered “guide fossils”.