Eutrephoceras dorbignyanum (Forbes in Darwin, 1846) - Strasbourg specimen

Eutrephoceras dekayi - Coon Creek Tennessee

''Eutrephoceras'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus of

nautilus The nautilus (, ) is a pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in t ...

from the

Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...

to the

Miocene The Miocene ( ) is the first 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 means "less recen ...

(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 The Southeastern Pennsylvania Transportation Authority (SEPTA) is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly 4 million people in five coun ...

are averagely convex towards the tip. The

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

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 Trent may refer to: Places Italy * Trento in northern Italy, site of the Council of Trent United Kingdom * Trent, Dorset, England, United Kingdom Germany * Trent, Germany, a municipality on the island of Rügen United States * Trent, California, ...

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 ...

) are cited as evidence of

mosasaur Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Greek ' meaning 'lizard') comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Maastricht on th ...

predation Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...

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 The nautilus (, ) is a pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in t ...

, which includes the only extant

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

s of the genera ''

Allonautilus The genus ''Allonautilus'' contains two species of nautiluses, which have a significantly different morphology from those placed in the sister taxon ''Nautilus''. ''Allonautilus'' is now thought to be a descendant of ''Nautilus'', rendering the l ...

'' and ''

Nautilus The nautilus (, ) is a pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in t ...

''. They are part of the superfamily

Nautilaceae The Nautilaceae form one of five superfamilies that make up the Nautilida according to Bernard Kummel (1964), and the only one that survived past the Triassic. The Nautilaceae comprise six families: Nautilidae, Paracenoceratidae, Pseudonautilidae ...

, the only superfamily of nautiloids to survive past the

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

. ''Eutrephoceras'' are sometimes separated into the

monogeneric In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

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 campbelli'' *'' Eutrephoceras carolinensis'' Kellum 1926 *'' Eutrephoceras cookanum'' (Whitfield 1892) *'' 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 animals Eocene animals Oligocene animals Miocene animals Miocene genus extinctions Eocene animals of South America Prehistoric molluscs of North America