Phylum: Mollusca
Class: Cephalopoda
Order: Endocerida
Family: Endocertidae
Genus: Endoceras Hall, 1847
Cincinnatian Species: Endoceras proteiforme

Geologic Range
Middle Ordovician – Late Ordovician

Common Paleoecology
Endoceras is an extinct genus of nektobenthic carnivores

Identification in Hand Sample:

  • Conchs large, straight, with annuulations varying from low and closely spaced to well elevated and distinctly apart
  • Sutures straight, transverse
  • Siphuncle large, ventral holochoanitic
  • Endocones subcircular in cross section
  • Endosiphunclular tube thin

Geographic Occurrences

Published Description

Treatise on Invertebrate Paleontology, Part K, Mollusca 3 (1964):

  • Conchs large, straight, similar to Cameroceras, but with annuulations varying from low and closely spaced to well elevated and distinctly apart; cross section slightly depressed; sutures straight, transverse. Siphuncle large, ventral holochoanitic; endocones subcircular in cross section; thin endosiphunclular tube; apical part unknown.

McFarlan (1931):

  • Othocones with large, more or less eccentric siphuncle, the funnels extending only to the next preceding septum

Hall (1847):

  • I propose this term, at least provisionally, to include those species of the Orthocerata which have a large siphuncle, mostly lateral or eccentric, marked or ridged on the outer surface by the septa, which, from their oblique direction, give it the appearance of a tube with spiral lines. Within the siphuncle are one or more very elongated conical tubes, often one within another to the number of four or five.
  • The latter character is one of the essential features of Actinoceras of Brown; but the foundation of this name implies an impossibility, and requires a structure incompatible with the economy of the Orthocerata; and, therefore, for our specimens at least, we must substitute another.

E. proteiforme