These extinct shelled cephalopods ruled the ocean for 300 million years. But how they swam and shaped the seas remains a mystery. "Snake stones" or ancient sea creature? Credit: opacity/flickr/CC ...

A collection of fossil shells from marine snails and clams is challenging a theory that says the world’s deadliest mass extinction was accompanied by severe ocean acidification. Instead of showing ...

Unlike those examples, however, ammonites had protective outer shells – and those shells didn't maintain one consistent shape throughout the fossil record. Led by postdoctoral fellow David Peterman ...

Although ammonoids died out around the same time as most dinosaurs, new computer models are revealing how these marine animals moved through the water. Nobu Tamura via Wikicommons under CC BY 3.0 ...