If you've ever found a spiral-shaped fossil, chances are it could be an ammonoid. These creatures lived millions of years ago in the oceans, and their unique shells make them easy to spot in fossil collections. Ammonoids belonged to a group called cephalopods, which also includes modern squids and octopuses. Their name comes from the Egyptian god Ammon, who was often shown with ram's horns resembling the ammonoid shell’s spiral.
They thrived from the Devonian period, about 400 million years ago, until they went extinct around 65 million years ago, at the same time as dinosaurs. What makes ammonoids cool is their wide variety of shell shapes and sizes, from tightly coiled to more loosely spiraled forms. These shells act like natural time capsules, giving scientists clues about Earth's history, ancient seas, and the evolution of marine life.
For paleontologists, ammonoids are more than just fossils – they're key to understanding geological timelines. Because ammonoids evolved rapidly and spread across the world, their fossils help date the rock layers they’re found in. This makes ammonoids great “index fossils,” aiding us in piecing together Earth’s ancient past.
Aside from scientific value, ammonoids capture the imagination of fossil enthusiasts and collectors. Their intricate and often beautiful spirals remind us of the amazing complexity of ancient life. Next time you see a spiral fossil, think about the long journey it took through time, coming from these remarkable marine animals that once ruled the seas.
Paleontologists have rediscovered and redescribed *Epitornoceras baldisi*, an ammonoid cephalopod from the Devonian period, using fossils from the Chigua Formation in Argentina. This species, which lived around 383 million years ago, was previously categorized under *Tornoceras*. This marks the first South American record for the genus *Epitornoceras*.
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