Acleistoceratidae
Encyclopedia
The Acleistoceratidae, named by Flower in Flower & Kümmel 1950, is a family of oncocerids
that contains genera characterized by depressed (or rarely compressed) exogastric brevicones and cyrtocones (Sweet, 1964 K398) that range from the Middle Silurian to the Middle Devonian. The siphuncle is broadly expanded, and in some actinosiphonate.
The Acleistoceratidae are derived from Oncoceras (Oncoceratidae) through Amphycertoceras, independently of the Oonoceras
stock. The family is named for the genus Acleistoceras
. All told some 22 genera have been described.
Oncocerida
The Oncocerida comprise a diverse group of generally small nautiloid cephalopods known from the Middle Ordovician to the Mississippian ,in which the connecting rings are thin and siphuncle segments are variably expanded...
that contains genera characterized by depressed (or rarely compressed) exogastric brevicones and cyrtocones (Sweet, 1964 K398) that range from the Middle Silurian to the Middle Devonian. The siphuncle is broadly expanded, and in some actinosiphonate.
The Acleistoceratidae are derived from Oncoceras (Oncoceratidae) through Amphycertoceras, independently of the Oonoceras
Oonoceras
Oonoceras is an extinct genus of nautiloid molluscs from the Silurian.-References:* Dinosaurs to Dodos: An Encyclopedia of Extinct Animals by Don Lessem and Jan Sovak...
stock. The family is named for the genus Acleistoceras
Acleistoceras
Acleistoceras is a genus of the oncocerid, nautiloid family Acleistoceratidae that lived in the shallow seas that covered much of North America during the Devonian; living from 409—383.7 mya, existing for approximately .-Taxonomy:...
. All told some 22 genera have been described.