Original part coming from Morocco. It consists of the piece and its lid. It occurs in gross as it is extracted.
The trilobites1 (Trilobita, from the latin, "three-lobes") are a class of extinct arthropods, within the a subphylum Trilobitomorpha. They are the most characteristic of the (was primary) Paleozoic was fossils. Have been described almost 4,000 especies.2
They appeared in the Cambrian period (at the beginning of the Paleozoic, about 540 million years ago), and began to diversify already in the lower Cambrian. After the end of the Cambrian mass extinction only survived forms inhabiting pelagics, deep-water environments. During the Ordovician reached its maximum diversity and occupied almost all marine ecological niches. From the Silurian presented few changes, until in the middle and Upper Devonian crises suffered a significant reduction, extinguishing all orders except Proetida. During the Carboniferous period the representatives of the group are rare and restricted to reef environments. The latest trilobites, already only inhabitants of shallow waters, disappeared during the crisis of the Permo-Triassic boundary (approximately 250 million years ago). Therefore, its presence in the Earth lasted throughout the Paleozoic, more300 million years. Trilobites are so abundant and they have been so deeply studied, are probably the best known fossil animals group.
We initially considered ancestors of crustaceans (especially the cochineal from ground moisture, which shares certain characteristics in common) or even all arthropods (since they were the first to appear in the fossil record). Today are considered to be a separate group, separated from phasmatodea and chelicerates.