Crioceras is a genus of extinct cephalopods belonging to the family Crioceratidae, which lived during the Late Jurassic period, approximately 155 to 145 million years ago. These marine creatures were mollusks and are categorized as ammonoids, possessing a coiled external shell that is chambered.
The shell of a Crioceras is easily recognizable, typically displaying a high degree of coiling and intricate ornamentation. It typically features smooth, rounded whorls, and a narrow aperture. The chambers inside the shell were connected by a complex siphuncle system, allowing for buoyancy control. Crioceras shells were composed of calcite, a form of calcium carbonate.
Crioceras fossils are commonly found in various parts of the world, particularly in Europe, Africa, and North America. They are often recovered from sediments deposited in marine environments, such as limestone formations or shale.
Ammonoids, including Crioceras, played an important role in the Mesozoic marine ecosystem as they were a diverse and widespread group. They likely had a similar behavior to their modern relatives, the nautiloids, using their shell and tentacles for locomotion and capturing prey.
The study of Crioceras and other ammonoids provides valuable information for understanding the evolutionary history of cephalopods and the ancient marine environments they inhabited. They act as key index fossils used by paleontologists for biostratigraphy, aiding in the dating and correlation of rock layers.
