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 | |
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Obinautilus pulchra | |
Scientific classification | |
Domain: | Eukaryota |
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]
Two species are recognised in the genus.[4]