Genus: Cameroceras Conrad, 1842
Cincinnatian Species: Cameroceras inaequabile
Middle Ordovician – Late Ordovician, ?Middle Silurian
Cameroceras is an extinct genus of nektobenthic carnivores
Identification in Hand Sample:
- Conch may exceed a diameter of 20cm and a length of 200cm
- Siphuncle can be up to 10cm, at or near the shell wall and ventral in position
- Suture is a straight line and extends straight across the shell
- Endosiphuncular tube thin, situated in ventral part of siphuncle
- Endocones simple, hallow at the larger end, each with its point nestled in the base of the next cone toward the apex of the shell
Fossils of Ohio (1996):
- Conch large (may exceed a diameter of 20 cm); siphuncle large (up to half the diameter of the conch)
- The genus Cameroceras Conrad includes the largest orthoconic cephalopods known from the state. Individual shells can exceed 210 cm in length and 20 cm in diameter. Of course, only very rarely are more-or –less complete specimens found. More common are fragments less than 25 cm long.
- The siphuncle of Camerocerasalso is very large – it may be half the diameter of the shell. In most specimens the siphuncle is at or near the shell wall and ventral in position. The suture is essentially a straight line and extends straight across the shell.
- Specimens in limestone may be preserved in their original shape; the cross section is round or a bit depressed. Specimens in shale, on the other hand, may be crushed so that the shell is nearly flat.
- Camerocerasbelongs to a group of cephalopods technically called endoceroids or endocerids, after the order Endocerida, to which they belong. (In some publications they are called endoceratoids, after their subclass, Endoceratoidea.) These animals have siphuncular deposits called endocones. When the animal was alive, each endocone was hallow at the larger end, and the siphuncle contained a series of endocones, each with its point nestled in the base of the next cone toward the apex of the shell. In some cases the endocones are the only part of the shell preserved.
- In some specimens only part of the internal mold of the siphuncle remains. It may be difficult to differentiate these internal molds from individuals of other genera in which the entire shell is of a diameter similar to that of the siphuncle of Cameroceras. In specimens in which camerae are preserved, the sutures generally are perpendicular to the length of the shell, and septa extend through the specimen. However, on internal molds of the siphuncles of Cameroceras, the lines that mark the intersections of the siphuncle and the septa are inclined, and there are no septa within the mold. Another relatively common kind of preservation is the internal mold of the base of an endocone. Such an internal mold has no internal structure, except for the particles of the rock of which it is composed, and it can be a very sharp-pointed object.
- According to Frey (1989), Cameroceras inaequabile (Miller) is the species of the genus most commonly found in the Ordovician rocks in the state. In former years, specimens of Camerocerasgenerally were identified as Endoceras Hall and Endoceras proteiforme (Hall) was the most commonly cited species.
- There has been much confusion concerning the relationship of this genus, based on the apical end of a large endocerid from the Trenton Limestone of New York, and the genus Endoceras Hall, which is based on more adoral portions of a large endocerid from the same strata. A good discussion of these taxa was prepared by Flower (1955a). It has been suggested by a number of authors that Cameroceras trentonese, the type species for Cameroceras, was the apical end of one of the large endocerid species described by Hall in 1847. Since Conrad’s genus was named in 1842, his name would have priority over EndocerasHall, which would become a junior synonym of Cameroceras. Hall, however, did not designate a type species for his genus. Subsequently, Miller(1889) designated Endoceras annulatum Hall as the type species of Endoceras. This species differs from other large endocerids from the Trenton in possessing an annulated exterior. These annulated species , placed in the Cyclendoceras by Grabau and Shimer (1910), are properly referred to as true EndocerasHall. Similar large endocerids with smooth shell exteriors are currently placed in the genus Cameroceras Conrad.
Treatise on Invertebrate Paleontology, Part K, Mollusca 3 (1964):
- Large to extremely large, straight conchs with circular or somewhat depressed cross section; sutures simple and straight, or with very slight ventral lobe. Siphuncle as much as half diameter of conch at maturity, mostly marginal, less commonly submarginal to subcentral in position; septal necks holochoanitic; endocones simple; endosiphuncular tube thin, situated in ventral part of siphuncle. Nature of apical portion not known with certainty, may be identical with forms given generic names such as Nanno Clarke or Suecoceras Holm.
- Straight; siphuncle marginal; a longitudinal septum forming a roll or involution with the margin of the siphuncle.
- This singular genus is confined to the Trenton limestone, (Lower Silurian.)The shell from which the description is taken resembles an Orthoceras externally, but is contracted at intervals; the siphuncle is obliquely undulated, and joins the margin.