Paper Nautilus Octopus

This guy has most features similar to other octopi (a round head, eight legs, no fins) but rather than living in the deep ocean, it prefers to dwell close to the surface. It also has a special characteristic which has only recently evolved to these dudes, the formation of a paper-thin shell to protect it's eggs in. The egg case strangely resembles the shell of the extinct ammonites with it's spiral form and continuous ribs. It has been said that these octopi used to use old ammonite shells for their eggs then developed the ability to repair them, later to develop the ability of making their own shell. This theory's uncertain but makes sense to me!

Extinct Ammonite

 Right before laying her eggs, the mother secretes this shell and lays her eggs in the very end. She somehow gets air into a bubble in the shell to increase it's buoyancy then fits herself into it for shelter.

Paper Nautilus Shell

There's a large difference between the male and females. Males don't have the large dorsal tenticles which females use for making the shell, and males only mate once in their lifetime. Whereas females mate many times in their life. When they make, the male extends a modified arm containing sperm which attaches to the female and she keeps hold of it for a long time.

These octopi are pretty amazing creatures and sometimes lurk around New Zealand!