''Adamsoceras'' is a genus of actinocerids of the family

Wutinoceratidae The Wutinoceratidae are a family of early actinocerids defined by Shimazu and Obata in 1938Flower 1976. New American Wutinoceratidae with Review of Actinoceroid Occurrences in Eastern Hemisphere;PartI, Memoir 28; New Mexico Bureau of Mines and M ...

, with spheroidal

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 ...

segments like '' Ormoceras'', but having a reticular canal system like ''

Wutinoceras ''Wutinoceras'' is a genus of now extinct nautiloid cephalopods of the Wutinoceratidae family. It exhibits orthoconic actinocerids with ventral siphuncles composed of broadly expanded segments.Memoir 2, Studies of the Actinocerida, New Mexico ...

''. Adamsoceras has a slender, gently expanding, orthoconic

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses ** Thin-shell structure Science Biology * Seashell, a hard o ...

that is slightly broader than high, i.e. depressed, with close spaced septa that form ventral lobes and a siphuncle that is near the ventral margin. ''Adamsoceras'' is known from rocks of Whiterockian age (early Middle

Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. ...

) in Nevada, the Baltic, Tasmania, and Manchuria. It may have been derived from ''Wutinoceras'', or from a common ancestor, and gave rise to ''Ormoceras''. The genotype is ''Adamsoceras isabelae'' from the upper Pogonip Group in Ikes Canyon in the

Toquima Range The Toquima Range is a mountain range, located primarily in Nye County with a small extension into Lander County, in Nevada, United States. Most of the range is included within the Humboldt-Toiyabe National Forest. The range reaches a maximu ...

in Nevada.Flower R.H. 1957. Studies of the Actinoceratida, New Mexico Bureau of Mines and Mineral Resources (NMBMMR) Memoir 2, Socorro NM .

References

{{Taxonbar, from=Q4680497 Prehistoric nautiloid genera Actinocerida Middle Ordovician animals of North America Taxa named by Rousseau H. Flower Paleozoic life of Newfoundland and Labrador