Opalized ammonite fossils are some of the most unique and ... before their extinction around 66 million years ago. They were spiral-shelled creatures, closely related to modern cephalopods like ...

Nipponites mirabilis ammonites grew in an unusual knot shape, rather than in a typical spiral While ammonite shells are abundant in the fossil record, it was only recently that scientists have found a ...

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 ...