Ram's Horn Squid (Spirula spirula)

The ram's horn squid is uniquely characterized by its internal, chambered shell, which is coiled into a perfect spiral resembling a ram's horn. Unlike most modern squids that have lost their rigid shells, this structure is made of solid calcium carbonate.

The squid uses its rigid, chambered internal shell to regulate its buoyancy in the open water column. By pumping liquid in and out of the shell's chambers and replacing it with gas, it can precisely maintain its depth without expending energy to swim.

While the live animal lives in deep ocean waters, its rigid white internal shells frequently wash up on tropical and subtropical beaches around the world. Beachcombers often find these fragile, spiraling white shells, commonly known as "Spirula."

The ram's horn squid is the sole surviving member of the ancient family Spirulidae. It is considered a living fossil, representing a distinct evolutionary lineage of cephalopods that dates back millions of years.