Eutrephoceras
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Eutrephoceras Temporal range: Late Jurassic–Miocene |
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| Eutrephoceras depressum | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Order: | Nautilida |
| Family: | Nautilidae |
| Genus: |
†Eutrephoceras Hyatt, 1894 |
| Type species | |
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Nautilus dekayi Morton 1834 |
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| Species | |
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See text |
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See text
Eutrephoceras is an extinct genus of nautilus from the Late Jurassic to the Miocene (around 161 to 5 million years ago). They are characterized by a highly rounded involute shell with slightly sinuous suture patterns.
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 are averagely convex towards the tip. The siphuncle 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 Eutrephoceras fossils (such as E. campbelli, of the Trent River Formation in Vancouver) are cited as evidence of mososaur predation on this genus.
Eutrephoceras can be found in Late Jurassic to Miocene formations confirmed in many places in the earth, and many species are valid.
Eutrephoceras is classified under the family Nautilidae, which includes the only extant nautiloids of the genera Allonautilus and Nautilus. They are part of the superfamily Nautilaceae, the only superfamily of nautiloids to survive past the Triassic.Eutrephoceras are sometimes separated into the monogeneric family Eutrephoceratidae as first proposed by A.K. Miller in 1951, but most authors include it under Nautilidae.
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