Ammonite time period4/8/2023 ![]() ![]() In addition to the typical coiled shape, ammonites in the heteromorph group could be straight like a tusk, or helically coiled, or even shaped like a compressed paper clip. There was an amazing diversity in the variety of shapes and ornamentation of ammonites. The smallest ammonite species had shells less than an inch in size, but the larger, coiled species were huge-some reached more than 9 feet (3 meters) in diameter! ![]() As a counterbalance, some of the chambers had calcareous deposits acting as ballast. As the animal grew, the old chambers could be filled with gas or liquid, in order to regulate the animal's buoyancy in the water, much like buoyancy tanks in a submarine. The animal lived in the outermost chamber of the shell. These walls left distinct suture lines where they joined with the outer shell, making patterns that are important in ammonite classification. The shells of ammonites were divided into chambers by intricately folded walls or septae. Although we lack fossilized soft parts for ammonites, we assume their bodies were similar to those of the chambered Nautilus. The Nautilus has a fleshy head equipped with a beak and very well-developed eyes, clustered in the middle of tentacles used for catching prey. Pachydiscus caterinae is a large species of coiled ammonite, with shells measuring up to 3 feet (1 meter) in diameter.Īmmonites were free-swimming mollusks that had external shells that were either straight or coiled. Related to the living chambered Nautilus, ammonites are extinct members of the group of marine animals called cephalopods, which include such other living species as squid, cuttlefish, and octopi. Also from Salsipeudes and Santa Catarina, Mexico. Ammonites were probably found in all depths of the ancient oceans.Ĭarlsbad, La Jolla, and Point Loma, in California. ![]()
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