''Anthoceras'' is a genus of straight, annulated, proterocamerioceratid molluscs (Order

Endocerida Endocerida, from Ancient Greek ἔνδον (''éndon''), meaning "inside", and κέρας (''kéras''), meaning "horn", is an extinct nautiloid order, a group of cephalopods from the Lower Paleozoic with cone-like deposits in their siphuncle. End ...

) from the

Lower Ordovician The Early Ordovician is the first epoch of the Ordovician period, corresponding to the Lower Ordovician series of the Ordovician system. It began after the Age 10 of the Furongian epoch of the Cambrian and lasted from to million years ago, unt ...

, found in

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

, North-Western Australia, and

Siberia Siberia ( ; , ) is an extensive geographical region comprising all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has formed a part of the sovereign territory of Russia and its predecessor states ...

. The cross section is circular, the

siphuncle The siphuncle is a strand of biological tissue, tissue passing longitudinally through the mollusc shell, shell of a cephalopod mollusc. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the li ...

moderately large, and marginal. Segments are constricted (producing concave profiles in internal molds); septal necks hemichoantici to subholochoantic (reaching halfway to almost to the previous septum); connecting rings thick. Endocones are long and slightly asymmetric. This genus is based on the phragmocone, the chambered part of the

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 Science Biology * Seashell, a hard outer layer of a marine ani ...

; the apical and apertural ends are unknown.

References

* Curt Teichert, 1964. Endoceratoidea. Treatise on Invertebrate Paleontology, Part K. Geol Soc. of America and Univ of Kansas press. Teichert and Moore (eds) * Prehistoric nautiloid genera Fossil taxa described in 1954 Proterocameroceratidae {{paleo-nautiloidea-stub

See also

References