Trilobiten (of the griech.Dreilapper) were jointed animals in their physique which existed from the Kambrium into the Urmeeren of the planet earth to the end of the Perm until around 250 million years ago. You had a kalzitisches Exoskelett (primarily back). You already died out before the dinosaurs conquered the earth and are index fossils for the Paläozoikum (Palaeozoic) today. 

 

The Trilobiten were part of the first arthropods (Arthropoden), an animal tribe of hard-shelled creatures with a jointed physique and many legs working coordinately (which unfortunately have hardly ever remained unchanged fossilly) together with the aerials of the animals due to their composition. You form the extinct class of the Trilobita types consisting of today nine recognized orders more than 150 families, over 5,000 genres and more described as 15,000. Every year new types are found and determined. Around their early investigation Joachim Barrande made himself rightful. Your variety makes the Trilobiten the most divergent group under all extinct living beings.