Nautilus pompilius mm 170 XL Seashell Sea Snail Cephalopod Octopus Cuttlefish Squid

Nautilus pompilius mm 170 XL Seashell Sea Snail Cephalopod Octopus Cuttlefish Squid, adult specimen, only a piece, as in photos.
The periosteum is not in perfect condition, with a slight natural crack, as in photo.
Family: Nautilidae.
Common name: Chambered Nautilus or Pearly Nautilus.
Syn. Nautilus repertus.

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).