In the world of weird marine wash ups, a paper nautilus octopus definitely makes the highlights reel. While following up on a report of a stranded seal on Cape Town's Muizenberg beach earlier this month, Dr Tess Gridley of the environmental conservation organisation Sea Search, came across something entirely unexpected: a paper nautilus squirming in the shore-break.

Despite what its common name might have you believe, this creature is not actually a member of the nautilus clade – a group of pelagic marine molluscs. In fact, paper nautiluses are only distantly related to the cephalopods with whom they share a moniker. The recent washup is actually one of the world's weirdest octopuses, an animal more formally known as an argonaut.

These oceanic oddities prefer to spend their time far offshore and out of sight, which makes the recent discovery highly unusual.

"I found this lovely lady on Muizenberg Beach this week while out looking for a dead seal," Dr Gridley explained on Facebook. "After the spring tide, there were a lot of interesting washouts: mermaid purses [egg casings], pufferfish and this paper nautilus, which is a type of octopus. The female is much bigger than the male and secretes this special shell in which she lays her eggs. Normally pelagic species that are found near the water’s surface, these animals occasionally wash out, but when they do, their chances of survival are low. This lady, unfortunately, didn’t make it, despite our best efforts."

There's a lot about the lives of these strange animals that we're yet to discover, but we do know that their delicate shells help keep female argonauts afloat as they move through the water column. The shell is about twice the thickness of a human hair and acts like a ballast. The argonaut "gulps" air at the surface, which is then pushed into the shell to maintain buoyancy underwater.

Paper nautiluses are not very strong swimmers, so it's possible that a large swell brought on by the spring tide threw the octopus off course.

Top header image: Ewald Rübsamen - Die Cephalopoden/Wikimedia Commons