This incredible pyritized ammonite (_Speetoniceras sp._) was collected in the Volga River, Russia and dates to the Jurassic Period - 201 to 145 million years old.

It's a spectacular specimen: the shimmering, golden pyrite is elegantly balanced on both halves and stands out boldly. Certainly a stunning piece of natural history!

Ammonites have intrigued and fascinated humans for thousands of years. Many cultures - from Australian aboriginals to the ancient Egyptians - collected and treasured these prehistoric and beautiful fossils. Perhaps it has something to do with the Fibonacci spiral pattern of their shell, which mirrors the galaxies.

Ammonites belong to the mollusca phylum in a class known as cephalopods - "head-footed" creatures such as octopus and squid. They swam in ancient oceans from the Devonian Period, about 400 million years ago, to their extinction along with the dinosaurs in the Cretaceous Period, 65 million years ago.

Ammonites were free floating invertebrates that were attacked by plesiosaurs and mosasaurs, two groups of gigantic marine reptiles. One way that ammonites could avoid an attack was to quickly change their buoyancy levels, zig zagging and sinking rapidly.

These incredible prehistoric animals ranged in size from tiny species only a few centimetres in diameter to the monstrous Cretaceous ammonite,_ Parapuzosia seppenradensis_, which grew to about 3 meters and would probably of weigh close to 1500 kilograms!

Each half measures 12 x 10.6 x 1.7 inches / 30 cm x 27 x 4.4 cm and the combined weight is 14.3 lbs. / 7 kg.

This piece has been sliced and polished. No enhancement of colour.

Learn more about [pyritized fossils](http://www.fossilrealm.com/pages/learn-about-pyritized-fossils "Learn About Pyritized Fossils - Fossil Realm Educational Pages").