''Obinautilus'' is an
extinct
Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
genus of shelled
cephalopod
A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...
that has been variously identified as an
argonautid octopod[Martill, D.M. & M.J. Barker (2006). A paper nautilus (Octopoda, ''Argonauta'') from the Miocene Pakhna Formation of Cyprus. ''Palaeontology'' 49(5): 1035–1041. ] or a
nautilid.
[UMUT CM 08493: ''Obinautilus pulchra'' Kobayashi, 1954]
The University Museum, The University of Tokyo.[Eyden, P. (2010)]
Fossil Octopuses
TONMO. It is known from the
Late Oligocene
The Chattian is, in the geologic timescale
The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the pro ...
to
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58[Japan
Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...](_blank)
.
[Saul, L.R. & C.J. Stadum (2005). Fossil argonauts (Mollusca: Cephalopoda: Octopodida) from Late Miocene siltstones of the Los Angeles Basin, California. ''Journal of Paleontology'' 79(3): 520–531. ] 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.
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.
[Strugnell, J., J. Jackson, A.J. Drummond & A. Cooper (2006). Divergence time estimates for major cephalopod groups: evidence from multiple genes. ''Cladistics'' 22(1): 89–96. ]
Species
Two species are recognised in the genus.
*†''Obinautilus awaensis'' (originally described as ''Argonauta awaensis''
[Tomida, S. (1983). Two new fossil ''Argonauta'' and firstly discovered ''Aturia coxi'' Miller from the late Tertiary of Boso Peninsula, Japan. ''Muzunami-shi Fossil Museum Bulletin'' 10: 107–116.]) —
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58[Miocene
The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...](_blank)
)
Upper Senhata Formation of
Bōsō Peninsula, Japan
*†''Obinautilus pulcher'' (sometimes spelled ''O. pulchra''
) —
Late Oligocene
The Chattian is, in the geologic timescale
The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the pro ...
Nichinan Formation of Japan
References
Further reading
* Noda, H., K. Ogasawara & R. Nomura (1986). Systematic and paleobiogeographic studies on the Japanese Miocene argonautid “''Nautilus''” ''izumoensis''. ''University of Tsukuba, Institute of Geoscience, Science Reports, Section B, Geological Sciences'' 7: 15–42.
* Yanagisawa, Y. (1990). ''Bulletin of the Geological Survey of Japan'' 41(3): 115–127.
Argonautidae
{{octopus-stub