Ammonites ENG

Ammonites are an extinct group of formerly widespread marine cephalopods. Their distant relatives are for instance octopi, cuttlefish, and nautili. The first ones emerged in Early Paleozoic and the last species became extinct shortly after dinosaurs at the beginning of Paleogene. Some ammonites were among the biggest known cephalopods: the diameter of their spiral shells reached up to 3 metres, but there were also smaller ones, up to 1 centimetre. Ammonites formed solid shells, commonly spiral-shaped. The shells were either smooth or with ribs, nods, or spines. The shell commonly contained a number of chambers divided by thin walls. The chambers gradually grew; the growing ammonite always inhabited the first (biggest) chamber, while the rest were filled with gases or liquid. The ammonites were capable of changing the amount of these gases or liquid in order to float or move upwards and downwards in the water. The body was divided into head, pouch-like body, and 10 tentacles surrounding the mouth that served for locomotion and hunting of prey. Ammonites had perfectly developed sight and were excellent and fast swimmers, which made them feared predators. Their prey were fish, crustaceans, and other molluscs. Based on marks of teeth and bite marks on the shells, ammonoids were frequent prey of sharks and marine reptiles. For that reason, many ammonites developed protective coloration of their shells. Thanks to the fact that they were widespread and their shells have a characteristic shape, ammonites are often used for stratigraphic research. 

Ammonite fossils are frequently found in sediments of Bohemian Cretaceous Basin. In the Geopark, they are most commonly found around Jičín and Turnov.