Monotypic prehistoric cephalopod genera

Orthoceras, from Ancient Greek ὀρθός (orthós), meaning "straight", and κέρας (kéras), meaning "horn", is a genus of extinct nautiloid cephalopod restricted to Middle Ordovician-aged marine limestones of the Baltic States and Sweden. This genus is sometimes called Orthoceratites and misspelled as Orthocera, Orthocerus, or Orthoceros.

Proteroctopus, from Ancient Greek πρότερος (próteros), meaning "anterior", ὀκτώ (októ), meaning "eight", and πούς (poús), meaning "foot", is an extinct genus of cephalopod that lived in the Middle Jurassic, approximately 164 million years ago. It is only known from a single species P. ribeti. The single fossil specimen assigned to this species originates from the Lower Callovian of Voulte-sur-Rhône in France. It is currently on display at the Musée de Paléontologie de La Voulte-sur-Rhône. While originally interpreted as an early octopus, a 2016 restudy of the specimen considered it to be a bas

Tusoteuthis is an extinct genus of large enchoteuthine cephalopod that lived during the Cretaceous. Although often called a squid, it is now thought to be more closely related to modern octopuses. Although many specimens from the Western Interior Seaway of North America were described, at 2019, only one, poorly preserved specimen from Kansas is recognized as Tusoteuthis. One species, T. longa, is traditionally recognized. In 2019, due to the poor preservation of the holotype specimen, Tusoteuthis was considered likely to be a nomen dubium, and it was proposed that later described species are b

Syllipsimopodi is an extinct member of the cephalopod subclass Coleoidea originally interpreted to belong to the clade Vampyropoda, which includes octopuses (Octopoda) and vampire squids (Vampyromorphida). The type and only known species is Syllipsimopodi bideni, named in honor of US President Joe Biden, and to raise awareness of his climate change policies. The holotype fossil was found in the Bear Gulch Limestone deposit in the US state of Montana in 1988, and donated that year to the Royal Ontario Museum by B. Hawes, designated ROMIP 64897. The species lived during the (Carboniferous) Missi

Vampyronassa rhodanica ("vampire fish trap") is an extinct vampyromorph cephalopod known from around 20 fossils from the Lower Callovian (165–164 Ma) of La Voulte-sur-Rhône, Ardèche, France.

Palaeoctopus is an extinct genus of octopuses that lived during the Late Cretaceous. It contains one valid species, P. newboldi, which has been found in Lebanon.

Styletoctopus is an extinct genus of octopus. The genus consists of the single species Styletoctopus annae, which lived approximately 95 million years ago during the late Cenomanian, (early late Cretaceous). It was first discovered in 2009 by a team led by Dirk Fuchs of Freie University in the Hâqel and Hjoula localities in Lebanon. Very few octopus species appear in the fossil record, as octopuses consist of soft tissue that usually decomposes before it has time to fossilize.