Obinautilus
Extinct genus of molluscs
From Wikipedia, the free encyclopedia
Obinautilus is an extinct genus of shelled cephalopod that has been variously identified as an argonautid octopod[3][4][5][6][7][8] or a nautilid.[1][9][10][11][12] It is known from the Late Oligocene to Pliocene of Japan.[4] The shell is discoidal and very involute, with rapidly expanding and compressed whorls, fine radial ribs, a rounded venter with a shallow furrow, and almost closed umbilicus.
| Obinautilus | |
|---|---|
| |
| Obinautilus pulchra | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Order: | Octopoda |
| Family: | Argonautidae |
| Genus: | †Obinautilus Kobayashi, 1954[1] |
| Species | |
Based on the examination of O. pulcher fossils from the Oligocene, the Tremoctopus–Argonauta divergence has been estimated to have occurred at least 29 million years ago.[5]
Species
Two species are recognised in the genus.[4]
- †Obinautilus awaensis (originally described as Argonauta awaensis[2]) — Pliocene (possibly also latest Miocene[4]) Upper Senhata Formation of Bōsō Peninsula, Japan[6]
- †Obinautilus pulcher (sometimes spelled O. pulchra[5][11]) — Late Oligocene Nichinan Formation of Japan[6]
