They were formed through a geological process known as opalization, wherein organic material from ancient ammonite shells is replaced ... thrived in the sea. Their fossils can often be located ...

Based on the fossil record, ammonites came in a wide range of sizes and shapes, from smaller than an inch to as large as nine feet wide. Some ammonites had long, straight shells, while others had ...

Fossils found in the northern part of Hokkaido are a new type of ammonite, the once-ubiquitous spiral-shelled creatures that went extinct with the dinosaurs 65 million years ago, researchers said.

It also looks like the spiral shell of a conch. We do not know what animal it was which was thus changed into stone.' An ammonite fossil collected from more than 5,000 metres above sea-level in the ...

Ammonites were shelled cephalopods that died out about 66 million years ago. Fossils of them are found all around the world, sometimes in very large concentrations. The often tightly wound shells of ...