Pyritized Ammonite Half | Russia

Species : Spitonicerus versicolor Age: Middle Jurassic (174.1 - 163.5 Million Years Ago)  Location: Dubki Clay Quarry, Volga River Basin, Saratov Region, Russia  Specimen Size: approximately 11"×13" Ammonite fossil specimen with pyrite as its replacement mineral.  Ammonites are cut in half to expose their internal chambers, phragmocone, encrusted with pyrite crystals. Near Saratov beautiful pyritized ammonites are found in the Dubki clay quarry. These are found in the so-called Lamberti zone and come from the upper Callovian, part of the Middle Jurassic period. Originating from within the bactritoid nautiloids, the ammonoid cephalopods first appeared in the Devonian (circa 409 million years ago) and became virtually extinct at the close of the Cretaceous (66 Mya) along with the dinosaurs. The classification of ammonoids is based in part on the ornamentation and structure of the septa comprising their shells' gas chambers. Because ammonites and their close relatives are extinct,