Argonauts on the Fast Shell

There are two very similar mollusks, the chambered nautilus and the argonaut (which is often called the "paper nautilus" because of the female's paper-thin eggcase). In ancient Greek legends, Jason took fifty men to find the golden fleece on a ship called the Argo, so they were argonauts. This relative of the octopus was thought to sail in its own way. See how that works? People thought they stole the shells, the wicked little pirates, but no, they own the shells.

Argonauta argo, Comingio Merculiano, 1896
People have been baffled by the argonaut for a long time, but gradually, many of its secrets have been revealed. It uses a form of jet propulsion, and actively scoops air to control buoyancy. I should have said she, because only the females have the shells. Males were unknown until the 19th century, and being exceptionally small is a contributing factor to their lack of discovery. Reproduction is something that is quite unique. The argonaut is yet another example of the Master Engineer's skill, and frustrating to evolutionists.
The delicate shell of the argonaut, also known as the ‘paper nautilus’, has long featured in art, architecture, pottery and jewellery. Finding them washed up on the shore, sometimes with the octopus-like resident still inside, people since the ancient Greeks have speculated about what the shell might be for.
Aristotle proposed that the shell functioned as a boat, allowing the argonaut to sail on the water surface. ‘Argonaut’ means sailor (Greek ‘nautilus’, ναυτίλος) on the Argo (the ship of Greek mythology). The idea that argonauts raise their flanged dorsal tentacles as sails to catch the wind was widely accepted for over 2,000 years. But no-one ever observed them doing it.
To read the rest, click on "Amazing argonauts — Scientists finally discover how the female argonaut really uses its shell".