''Eutrephoceras'' 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

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 ...

from the

Late Jurassic The Late Jurassic is the third Epoch (geology), epoch of the Jurassic Period, and it spans the geologic time scale, geologic time from 161.5 ± 1.0 to 143.1 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic stratum, strata.Owen ...

to the

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 ...

(around 161 to 5 million years ago). They are characterized by a highly rounded involute shell with slightly sinuous suture patterns.

Description

''Eutrephoceras'' typically possess nearly globular conchs (shells). The whorls are reniform (kidney-shaped) in cross section and broadly rounded on the sides and lower edge. On the upper edge it is only slightly curved. The surface of the shell is usually smooth, but can sometimes be sculptured. The suture patterns are slightly sinuous, though it can be more or less straight in some species. The umbilicus is small and barely noticeable, sometimes hidden altogether. The

septa SEPTA, the Southeastern Pennsylvania Transportation Authority, is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly four million people througho ...

are averagely convex towards the tip. 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 small and circular in cross section. It can vary in position considerably and its placement is important in identifying different species under the genus, but it is never marginal. Puncture marks made by teeth on several Late Cretaceous-aged ''Eutrephoceras'' fossils (such as ''E. campbelli'', of the Trent River Formation in

Vancouver Vancouver is a major city in Western Canada, located in the Lower Mainland region of British Columbia. As the List of cities in British Columbia, most populous city in the province, the 2021 Canadian census recorded 662,248 people in the cit ...

) are cited as evidence of

mosasaur Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Ancient Greek, Greek ' meaning 'lizard') are an extinct group of large aquatic reptiles within the family Mosasauridae that lived during the Late Cretaceous. Their first fossil remains wer ...

predation Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

on this genus.Ludvigsen, Rolf & Beard, Graham. 1997. West Coast Fossils: A Guide to the Ancient Life of Vancouver Island. pg. 117

Distribution

''Eutrephoceras'' can be found in

formations confirmed in many places in the earth, and many species are valid.

Taxonomy

''Eutrephoceras'' is classified under the family

Nautilidae 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 ...

, which includes the only extant

nautiloid 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 ...

s of the genera ''

Allonautilus The genus ''Allonautilus'' contains two species of nautiluses, which have a significantly different Morphology (biology), morphology from those placed in the sister taxon ''Nautilus (genus), Nautilus''. Mitogenome comparisons between ''Allonautil ...

'' and ''

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 ...

''. They are part of the superfamily Nautilaceae, the only superfamily of nautiloids to survive past the

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

. ''Eutrephoceras'' are sometimes separated into the monogeneric family Eutrephoceratidae as first proposed by A.K. Miller in 1951, but most authors include it under

. Species under ''Eutrephoceras'' include the following. This list is incomplete. *'' Eutrephoceras antarcticum'' Landman ''et al.'', 2004 *'' Eutrephoceras berryi'' Miller 1947 *'' Eutrephoceras bryani'' (Gabb 1877) *'' Eutrephoceras carolinensis'' Kellum 1926 *'' Eutrephoceras dartevellei'' Miller, 1951 *'' Eutrephoceras dekayi'' (Morton 1834) (type) *'' Eutrephoceras dorbignyanum'' (Forbes ''in'' Darwin, 1846) *'' Eutrephoceras eyerdami'' Palmer, 1961 *'' Eutrephoceras hallidayi'' (Waring 1914) *'' Eutrephoceras hannai'' Vokes 1937 *'' Eutrephoceras japonicum'' (Shimizu 1926) *'' Eutrephoceras johnsoni'' Miller 1947 *'' Eutrephoceras jonesi'' Miller and Thompson 1933 *'' Eutrephoceras laverdei'' Durham, 1946 *'' Eutrephoceras marksi'' Miller 1947 *'' Eutrephoceras oregonense'' Miller 1947 *'' Eutrephoceras reesidei'' Stenzel 1940 *'' Eutrephoceras simile'' Spath 1953 *'' Eutrephoceras sloani'' Reeside 1924 *'' Eutrephoceras sphaericum'' (Forbes 1846) *'' Eutrephoceras stephensoni'' (Dickerson 1914)

References

External links

{{Taxonbar, from=Q3866777 Nautiluses Prehistoric nautiloid genera Oxfordian first appearances Jurassic molluscs Cretaceous cephalopods Paleocene molluscs Eocene molluscs Oligocene molluscs Miocene molluscs Miocene genus extinctions Eocene animals of South America Prehistoric molluscs of North America Prehistoric molluscs of Europe