''Cassinoceras'' ("Cassin Horn") is a genus of

nautiloid Nautiloids are a group of marine cephalopods ( Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and ''Allonautilus''. Fossil nautiloids are diverse and speciose, with over 2,500 recorded species ...

s belonging to the

endocerid Endocerida is an extinct Nautiloidea, nautiloid order, a group of cephalopods from the Lower Paleozoic with cone-like deposits in their siphuncle. Endocerida was a diverse group of cephalopods that lived from the Early Ordovician possibly to the ...

family

Piloceratidae The Piloceratidae are a compressed, rapidly expanding, cyrtoconic brevicones with holochoanitic ventral siphuncles and simple endocones. Most likely evolved from ''Clitendoceras'', a narrow, slightly endogastric genus intermediate in form between ...

that comes from the late

Early 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. ...

of eastern North America and adjacent territories.Teichert, Curt, 1964. Endoceratoidea ''in''

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology'' (or ''TIP'') published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and co ...

Part K Mollusca 3; Geological Soc. of America and Univ of Kansas Press; pp K171-K172, Piloceratidae. ''Cassinoceras'' is characterized by short, laterally compressed, rapidly expanding shells in which the upper, dorsal, surface has a convex curvature and diverges strongly from the essentially straight lower, ventral surface. The

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 ...

which entirely fills the apical portion at the back of the shell is also compressed and vertically expanding, and is filled with simple endocones with a complex system of endosiphuncular blades through which a flattened endosiphuncular tube with widely spaced partitions runs. The shell of ''Cassinoceras'' grew to about 25 to 30 cm long.Moore, Raymond C., Lalicker, Cecil G., & Fischer, Alfred G. 1952. ''Invertebrate Fossils''. McGraw-Hill, New York. Page 355 ''Cassinoceras'' was named by Ulrich & Foerste in 1936 for the Fort Cassin Limestone of western

Vermont Vermont () is a state in the northeast New England region of the United States. Vermont is bordered by the states of Massachusetts to the south, New Hampshire to the east, and New York to the west, and the Canadian province of Quebec to ...

, from which the upper stage of the

Canadian Epoch The Canadian is the Lower or Early Ordovician in North America. The term is common in the older literature and has been well understood for more than a century. However it has no official recognition by the International Commission on Stratigraphy ( ...

, known as the Cassinian gets its name. The genotype is ''Cassinoceras explanator'' (Whitfield). A second species ''Cassinoceras grande'' Ulrich & Foerste is also known from the Fort Cassin Limestone. The genus has also been found in

Newfoundland Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...

, the Arctic islands, and on

Spitsbergen Spitsbergen (; formerly known as West Spitsbergen; Norwegian: ''Vest Spitsbergen'' or ''Vestspitsbergen'' , also sometimes spelled Spitzbergen) is the largest and the only permanently populated island of the Svalbard archipelago in northern Norw ...

References

Prehistoric nautiloid genera Ordovician cephalopods Ordovician cephalopods of North America Paleozoic life of Newfoundland and Labrador Fossil taxa described in 1936 {{paleo-nautiloid-stub