See text Eutrephoceras is an extinct genus of nautilus from the Late Jurassic to the Miocene (around 161 to 5 million years ago).

The whorls are reniform (kidney-shaped) in cross section and broadly rounded on the sides and lower edge.

[2] Puncture marks made by teeth on several Late Cretaceous-aged Eutrephoceras fossils (such as E. campbelli, of the Trent River Formation in Vancouver) are cited as evidence of mosasaur predation on this genus.

[3] Eutrephoceras can be found in Late Jurassic to Miocene formations confirmed in many places in the earth, and many species are valid.

[2] Eutrephoceras is classified under the family Nautilidae, which includes the only extant nautiloids of the genera Allonautilus and Nautilus.