Aegasteroceras sagittarium Ammonite | England

Aegasteroceras sagittarium Lower Jurassic, Lower Lias (200 million years old) Conesby Quarry, Scunthorpe, Lincolnshire, England Frodingham Ironstone Formation Remaining Ammonite approx. size: 4" x 3.25" Entire Ammonite approx. size: 7.5" x 6" Matrix approx. size: 9.25" x 8.5" x 2" Approx. weight: 4 lbs. 3 oz. The shell of this ammonite has been naturally replaced by calcite. You can see the calcite crystals at a removed portion of the shell. Ammonoids are a group of extinct marine mollusk animals in the subclass Ammonoidea of the class Cephalopoda. These mollusks, commonly referred to as ammonites, 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 vanished in the Cretaceous–Paleogene extinction event. Ammonites are excellent index fossils, and it is often possible to link the rock layer in which a partic