Scunthorpe Ammonite | Aegasteroceras sagittarium | England

Aegasteroceras sagittarium Lower Jurassic (200 million years old) Conesby Quarry, Scunthorpe, Lincolnshire, England Frodingham Ironstone, Obtusum Zone   Specimen approx. size: 4.5" x 3.5" x 1.75" Matrix approx. size: 5.25" x 5" x 2.25"   The shell of this ammonite has been replaced by calcite, which contrasts nicely with some of the sutures. The base of the rock has been cut flat for aesthetic presentation without the need for a display stand.   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 particu