''Heminautilus'' 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 nautiloids from the nautilacean family Cenoceratidae that lived during the

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

. Fossils of ''Heminautilus'' have been registered in rocks of Barremian and

Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...

age.''Heminautilus''
at

Fossilworks Fossilworks was a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cr ...

.org

Nautiloids Nautiloids are a group of cephalopods (Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and ''Allonautilus''. Fossil nautiloids are diverse and species rich, with over 2,500 recorded species. Th ...

are a subclass of shelled

cephalopods 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 were once diverse and numerous but are now represented by only a handful of species. ''Heminautilus'' has a discoidal compressed involute shell with flanks converging on a narrow flattened outer margin, the venter. Whorls are higher than they are wide. The suture is sinuous with a ventral lobe, subtriangular saddles on the ventral shoulders, broad lateral lobes, and narrow rounded saddles on the umbilical shoulders. The

siphuncle The siphuncle is a strand of biological tissue, tissue passing longitudinally through the mollusc shell, shell of a cephalopod mollusc. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the li ...

is subcentral., 1964

Species

The following species of ''Heminautilus'' have been described: * ''H. boselliorum'' * ''H. etheringtoni'' * ''H. japonicus'' * ''H. lallierianus'' * ''H. rangei'' * ''H. sanctaecrucis'' * ''H. saxbii'' * ''H. stantoni'' * ''H. tejeriensis'' * ''H. tyosiensis'' * ''H. verneuilli''

Distribution

Fossils of ''Heminautilus'' have been found in Bulgaria, Colombia (at

Caballos Formation The Caballos Formation (, KI) is a geological formation of the Upper Magdalena Valley (VSM), Caguán-Putumayo Basin, Central and Eastern Ranges of the Colombian Andes. The sandstone and shale formation dates to the Middle Cretaceous period; Ap ...

, Boyacá, Tolima and

Une Formation The Une Formation (, Kiu) is a formation (geology), geological formation of the Altiplano Cundiboyacense, Cordillera Oriental (Colombia), Eastern Ranges of the Colombian Andes. The predominantly sandstone formation dates to the Cretaceous, Middle ...

),Baudouin et al., 2016, p.87 Egypt,Baudouin, 2016, p.76 France, Hungary,Baudouin, 2016, p.66 Japan, Mexico, Spain, Switzerland, Tunisia,Baudouin, 2016, p.72 the United Kingdom, the United States (Arkansas), Venezuela.

References

Bibliography

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Species

Distribution

See also

References

Bibliography

Further reading