Systematic Paleontology
Class: Cephalopoda
Subclass: Nautiloidea
Order: Oncocerida
Family: Onchoceratidae
The Oncoceratidae is a family of oncocerid nautilids, established by Hyatt in 1884, with a stratigraphic range extending from the middle Ordovician to the upper Silurian.
Shells are exogastric brevicones and cyrtcones, some being sort others elongate, with the ventral side outwardly arched. Most are laterally compressed, although a few species are circular or dorso-ventrally depressed in section.
Siphuncles in the early stages of early forms are tubular and orthochoanitic, but in later stages and throughout later forms are cyrtochoantic with expanded segments. Connecting rings are thin. Inwardly directed planar actinosiphonate depostis are found in the siphuncles of a few advanced members.
The Oncoceratidae contains some 24 named genera. Representative examples include Beloitoceras, Digenuoceras, Miamoceras, Oocerina, Richarsonoceras, and Rizosceras
References
Walter C. Sweet, 1964. Nautiloidea- Oncocerida. Treatise on Invertebrate Paleontology, Part K. Oncoceratidae K283 -K290