Adventures of the argonaut

If for no other reason, I love the American Museum of Natural History because it contains a web of seemingly endless nooks and crannies to explore. One, just far enough away from the main exhibit halls to go unnoticed by most visitors (it is not even denoted on the museum map anymore), is a collection of seashells from a time when neatly-arrayed collections of specimens set in place next to their identification labels formed the core of natural history museums. Most are relatively familiar, curled houses without their occupants, but there is one which immediately grabbed my attention the first time I saw it - an argonaut, complete with a reconstruction of the squishy organism which lived inside the shell.

At first I had no idea whether I was looking at a living creature or some recently-extinct cephalopod "brought to life" in the museum's collection. I knew of squid, octopus, cuttlefish, and the pearly nautilus, but no book I had ever read mentioned the shelled argonaut. Even after I stumbled across it at the AMNH I rarely heard anything about it, but this week the argonaut is getting a bit more press. Scientists have now discovered how the argonaut uses its shell to achieve neutral buoyancy, and you can read all about it in Ed Yong's excellent summary at Not Exactly Rocket Science.