''Nautilus cookanus'' 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 ...

species of

nautilus A nautilus (; ) is any of the various species within the cephalopod family Nautilidae. This is the sole extant family of the superfamily Nautilaceae and the suborder Nautilina. It comprises nine living species in two genera, the type genus, ty ...

. It lived during the

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided b ...

. ''N. cookanus'' placed within the genus ''Nautilus'', together with extant species based on their shared shell characters.Ward, P.D. & W.B. Saunders 1997
''Allonautilus'': a new genus of living nautiloid cephalopod and its bearing on phylogeny of the Nautilida
''Journal of Paleontology'' 71(6): 1054–1064. Fossils of the species from the

Late Eocene The Priabonian is, in the International Commission on Stratigraphy, ICS's geologic timescale, the latest age (geology), age or the upper stage (stratigraphy), stage of the Eocene epoch (geology), Epoch or series (stratigraphy), Series. It spans ...

Hoko River Formation are noted as one of the two oldest occurrences for the genus (with the other, older occurrence being '' N. praepompilius'' of the

Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...

). Its name has frequently been misspelled as "''cookanum''".

References

Prehistoric nautiloids Nautiluses Eocene molluscs Eocene animals of North America Fossil taxa described in 1892 {{paleo-Nautiloidea-stub