ammonit

Ammonit is a common name for an extinct group of marine molluscs, part of the subclass Ammonoidea. These cephalopods were characterized by their coiled shells, which were typically planispiral, meaning they were coiled in a flat spiral. The shells were divided into chambers by internal walls called septa. The ammonit lived in the gas-filled chambers of its shell, with a tube called a siphuncle connecting all the chambers, allowing it to control its buoyancy by regulating the amount of gas or liquid in the chambers. Ammonites first appeared in the Devonian period and became extinct at the end of the Cretaceous period, along with the dinosaurs. They were incredibly diverse, with over 10,000 known species, and their shells are found as fossils worldwide. Their distinctive shells make them popular among fossil collectors and important index fossils for dating rock strata.