Streptoceras
Introduction '''''Streptoceras''''' is a genus in the extinct oncocerid family Acleistoceratidae that plied the shallow sea floor from the Middle Silurian to the Middle Devonian. ''Streptoceras'' is characterized by a shell that is large but short in proportion (breviconic) with the ventral profile convex and dorsal profile concave in the posterior part, convex over the body (or living) chamber, then concave toward the front, like ''Amphycertoceras'', but with a triangular shaped aperture. ''Streptoceras'' is found in the Middle Silurian of North America, in Ontario. Oncocerids (Order Oncocerida) were Nautiloid cephalopods that lived during the early part of the Paleozoic Era. They are closely related to the Nautilids that include the living ''Nautilus'', but on a different evolutionary branch.
See also * Nautiloid** List of nautiloids
References * Sweet, W.C. 1964; Nautiloidea—Oncocerida, in the Treatise on Invertebrate Paleontology; Geological Society of America and University of Kansas press* Sepkoski, J.J. Jr. 2002.A compendium of fossil marine animal genera. D.J. Jablonski & M.L. Foote (eds.). ''Bulletins of American Paleontology'' '''363''': 1–560.Sepkoski's Online Genus Database (CEPHALOPODA)