The ammonites represent an extinct group with a large number of species of exclusively sailor, fossil cephalopod (Cephalopoda). Over 1500 genres are known, the number of the types might be within the range of about 30-40,000. The size of the shell of fully-grown animals usually is in the area of centimetres, Pachydiscus seppenradensis is to a 2 metres way known the greatest till now. Partly the temporal delimitation sailor sediments is carried out or was carried out exclusively on ammonites put for ammonites die out at the end of the chalk of their first appearance in the Devon up to hers a large number of the index fossils. You therefore are in geology and paleontology of great importance. Due to their beauty, variety and frequency they are also popular with many Fossiliensammlern and can be found appropriately frequent in the Fossilienhandel.