Trilobite, Calymene or Diacalymene ca. 5-8 cm, Morocco

Trilobites predate the dinosaurs. They appeared early in the Cambrian and became extinct at the end of the Permian, about 250 million years ago... They are probably so well preserved because of their hard outer shell. In few places in the world have they been found with soft parts remaining. Depending on the locally specific mineral composition and the structure of the fossiliferous layers, they have different rock composition, surface structure, color, etc. These are often glued together because they are easily broken during excavation. The name trilobite means three lobes. The trilobite is also divided lengthwise into 3 parts; cephalon (head), thorax (body) and pygidium (back) Trilobites were articulated fossils and are said to be the first animals to develop eyes. They had compound eyes and lived on the sea floor. It has been called the Cambrian explosion, because shell-bearing fossils are found from layers from the Cambrian (approx. 540 million) and it is at that time that biological development on Earth is said to have started. The Devonian is said to be a peak period for trilobites, where they are seen to have developed widely across the Earth. Some fossils that lived for a limited period of time can be compared in geological strata, in which case they are called lineage fossils. If an animal, such as the trilobites, left marks behind and these were fossilized, these are called trace fossils. Another name for trace fossils is rusophycus. One species is called Diacalymene ouzregui Ordovician ( ca. 450 million years ) Morocco Erfoud, Morocco