Jeanne and the Argonauts: Unwrapping the Secret Life of the Paper Nautilus

Solving the Mystery of the Argonaut’s Shell

Sicily. Photo by Samuel Ferrara on Unsplash

Pale and brittle, its surface rippled like a snap-frozen ocean, the paper nautilus shell is familiar both as a curio and a collector’s item. But the animal that occupies it — a type of octopus called Argonauta — is not as well-known. For two thousand years, ever since Aristotle wrote about them in his History of Animals, two things were certain about the paper nautilus.

It used a pair of expanded arms as sails…

In between its feelers it has a[n]…amount of web-growth, resembling the substance between the toes of web-footed birds; only that with these latter the substance is thick, while with the nautilus it is thin and like a spider’s web. It uses this structure, when a breeze is blowing, for a sail, and lets down some of its feelers alongside as rudder-oars.

…and the shell it occupied was made by another animal.

Neither of these certain things is true.

Argonauta from The Hall of Shells by Mary Earle Hardy. Image from Biodiversity Heritage Library. Public Domain.

Two Certain Things