Argonauta argo (1) mm 113 Seashell Sea Snail Cephalopod Octopus Paper Nautilus

Argonauta argo mm 113 Seashell Sea Snail Cephalopod Octopus Paper Nautilus, female Shell, only a piece, as in photos.
Family: Argonautidae.
Common name: The Greater Argonaut.
Syn. Argonauta papyracea, Argonauta grandiformis, Argonauta striata, Ocythoe antiquorum, Trichocephalus acetabularis, Todarus argo, Argonauta minor, Argonauta naviformis, Argonauta papyria, Argonauta bulleri, Argonauta cygnus, Argonauta ferussaci, Argonauta monterosatoi, Argonauta sebae.

Characteristic element of the species is the sexual dimorphism: the female can reach 20 cm in length, while the male does not exceed one centimeter. During the fertile period, the female secretes a calcareous ootheca, similar to a shell, with very thin walls, like paper, in which she lays fertilized eggs.

The genus Nautilus and Argonauta, cephalopods tetrabranchiata (in contrast to cuttlefish, octopus and squid that are dibranchiata) are the last descendants of the Ammonites, that large group of molluscs with a spiral shell that populated the prehistoric seas millions of years ago. From Belemnites, on the contrary, are derived the dibranchiata on cited, having incorporated the outer shell just inside the body (the cuttle bone is the remains).