(Internal #F-424-X) You are bidding on this natural, Ammonite, from the Upper Cretaceous, 120 million years old. Average between 1-1/8" to 1-1/2" diameter. Locality: SOUTH DAKOTA, USA Stratigraphy: PIERRE SHALE Ammonites went exticnt with the dinosaurs, and are marine animals in the subclass: Ammonoidea, class: Cephalopoda, and phylum: Mollusca. Ammonites are excellent index fossils, making it easier to link the rock layers to a specific time period of which they are found. Ammonites' closest living relatives are the octopus, squid, and cuttlefish. Click on our Store tag for similar items. WE SHIP WORLDWIDE, see the chart for postage to your country.