An artists impression of a Mosasaur


Imagine a swirling seashell, like a tightly coiled ram's horn. That's an ammonite, a fascinating creature that lived in Earth's oceans millions of years ago! Ammonites were part of a group of animals called cephalopods, which are relatives of today's octopuses, squids, and cuttlefish. Unlike their modern kin, ammonites had beautiful external shells that spiraled outwards, growing larger as the animal matured.

These spiral shells weren't just for show. Ammonites actually lived inside them, with their soft bodies occupying the largest chamber. As they grew, they would add new, bigger chambers onto their shell and wall off the older ones with special partitions called septa. This clever design allowed them to maintain buoyancy and move through the water efficiently.

Ammonites were incredibly successful for a very long time. They first appeared in the oceans around 200 million years ago and thrived for 140 million years! Their reign came to an end alongside the dinosaurs about 66 million years ago. Thankfully, ammonites left behind a remarkable legacy – their fossils! Because their shells were so hard and mineral-rich, they often withstood the pressures of time and became beautifully preserved.

Fossil hunters around the world can still find ammonites today. These fossils come in all shapes and sizes, with some as small as a marble and others as wide as car tires! Studying ammonite fossils helps scientists understand what these ancient creatures looked like, how they lived, and the dramatic changes that have unfolded on our planet over millions of years.