The animals constantly grew new shell material as they aged ... Scientists believed that ammonites, like modern cephalopods, had soft body tissue with tentacles attached to their heads for ...

a mother-to-be holds on to the rocky substrate as water flows over her shell. The animal is about one inch long and protected by a whorled casing that covers her soft body. She is a gastropod ...

Instead, hermit crabs have a hard exoskeleton on the front part of their bodies but a soft tail on the other half, which they protect using the discarded shells of other animals, like whelks.