Bulletin de la Société belge de géologie, de paléontologie et d'hydrologie (1892) (19815449423)

Ammonoidea, commonly known as ammonites, were a diverse group of marine mollusks that existed from the Devonian period to the end of the Cretaceous period, spanning a time frame of approximately 400 million years. They were part of the class Cephalopoda, which also includes modern-day octopuses, squids, and nautiluses. Ammonites were characterized by their coiled shells, which could range from a few centimeters to over two meters in diameter in some species. These shells often displayed intricate patterns of ridges, spines, and chambers. The chambers were interconnected by a tube called a siphuncle, which the animal used to regulate its buoyancy. These creatures were highly successful in their evolutionary history and occupied a variety of ecological niches in oceans worldwide. They were active predators, using their tentacles to capture prey, much like modern-day squids. Despite their success, ammonites, along with many other marine organisms, became extinct at the end of the Cretaceous period, likely due to the catastrophic event associated with the Chicxulub asteroid impact and subsequent environmental changes.

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