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For other uses, see Ammonite (disambiguation). Temporal range:
400–66 Ma Asteroceras BW.jpg Artist's reconstruction of
Asteroceras Scientific classification e Kingdom: Animalia
Phylum: Mollusca Class: Cephalopoda Subclass: Ammonoidea Zittel,
1884 Orders and Suborders  See text  Ammonites /ˈæmənts/ are an
extinct group of marine mollusc animals in the subclass
Ammonoidea of the class Cephalopoda. These molluscs are more
closely related to living coleoids (i.e., octopuses, squid, and
cuttlefish) than they are to shelled nautiloids such as the
living Nautilus species. The earliest ammonites appear during
the Devonian, and the last species died out during the
Cretaceous–Paleogene extinction event.  Ammonites are excellent
index fossils, and it is often possible to link the rock layer
in which a particular species or genus is found to specific
geological time periods. Their fossil shells usuall