Ammonitess

Ammonites were a diverse group of extinct marine molluscs belonging to the subclass Ammonoidea. They are closely related to modern-day cephalopods, such as squid and octopuses, and are more distantly related to the nautilus. Ammonites first appeared in the Devonian period, around 400 million years ago, and became extinct at the end of the Cretaceous period, approximately 66 million years ago, along with the dinosaurs. Their fossilized shells are commonly found and are often collected as treasures.

The most distinctive feature of ammonites is their coiled shell, which typically grew in a flat spiral. This shell was divided into chambers by internal walls called septa. The ammonite lived in the outermost chamber, while the inner chambers were filled with gas and liquid, allowing them to control their buoyancy and swim in the water column. The shape and ornamentation of these shells varied greatly among different species, providing important clues for paleontologists classifying them. Some had smooth shells, while others featured intricate ribs, spines, or tubercles.

Ammonites were a widespread and successful group, inhabiting oceans worldwide throughout the Mesozoic Era. They occupied a variety of ecological niches, from free-swimming predators to benthic dwellers. Their fossils are abundant in sedimentary rocks and are valuable index fossils, meaning their presence helps date rock layers. The sudden extinction of ammonites, alongside many other species, is linked to the K-Pg extinction event, widely believed to have been caused by a massive asteroid impact.