''Cameroceras'' ("chambered horn") is a genus of extinct, giant

orthoconic An orthocone is an unusually long straight shell of a nautiloid cephalopod.; During the 18th and 19th centuries, all shells of this type were named '' Orthoceras'', creating a wastebasket taxon, but it is now known that many groups of nautiloids ...

cephalopod that lived mainly during the

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. T ...

period. It first appears during the middle Ordovician, around 470 million years ago, and was a fairly common component of the fauna in some places during the period, inhabiting the shallow seas of

Laurentia Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, althoug ...

Baltica Baltica is a paleocontinent that formed in the Paleoproterozoic and now constitutes northwestern Eurasia, or Europe north of the Trans-European Suture Zone and west of the Ural Mountains. The thick core of Baltica, the East European Craton, ...

and

Siberia Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive region, geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a ...

.Frey, R.C. 1995. U.S. Geological Survey, p.73 Its diversity and abundance became severely reduced following the Ordovician–Silurian extinction events, and the last remnants of the genus went extinct sometime during the Wenlock. In older literature ''Cameroceras'' was treated as the largest nautiloid with shell length about or even , however the large-sized species is no longer belong to genus ''Cameroceras'' but ''

Endoceras ''Endoceras'' (Ancient Greek for "inner horn") is an extinct genus of large, straight shelled cephalopods from the Middle and Upper Ordovician that gives its name to the Nautiloid order Endocerida. The cross section in the mature portion is slig ...

giganteum'', and the -long specimen is highly doubtful.

Description

''Cameroceras'' is a cephalopod, a taxon of molluscs that includes the octopuses, squids and cuttlefish. From comparison with living cephalopods, particularly the shelled chambered nautilus, some inferences about the biology of ''Cameroceras'' can be made. The head of the animal would have been soft muscular tissue situated at the opening of the hard cone-like shell, with the mantle (main body) lying within the shell for protection. Tentacles would have grown from the base of the head like in a modern nautilus, and these tentacles would have been used to seize and manipulate prey. At the base of these tentacles within the buccal mass (analogous to the mouth) a hard keratinous beak would have bitten into the bodies of its prey, and is assumed to have been strong enough to breach the prey's exoskeleton or shell. Within the beaks of modern cephalopods a radula, or 'toothed' tongue is used to rasp out soft tissue from within the prey's shell.

Taxonomic usage

''Cameroceras'' has become a "

wastebasket taxon Wastebasket taxon (also called a wastebin taxon, dustbin taxon or catch-all taxon) is a term used by some taxonomists to refer to a taxon that has the sole purpose of classifying organisms that do not fit anywhere else. They are typically defined ...

" in which large orthoconic endocerids such as ''

'', '' Vaginoceras'', and ''

Meniscoceras ''Meniscoceras'' is a straight and slender Chazyan endocerid described by Rousseau Flower in 1941 The genus was originally included in the Proterocameroceratidae (Flower, 1955) but later (Flower, 1976) placed with its predecessor, '' Najaceras ...

'' were originally placed. This makes it extremely difficult to describe ''Cameroceras'' as a distinct genus. Although the type species ''Cameroceras trentonense'' was first described by Conrad in 1842, since then the generic term has had variable meaning. Hall, who named and described ''Endoceras'' in 1847 recognized ''C. trentonense'' specifically, but used ''Endoceras'' for other specimens of large endocerids from the Trenton Limestone of western New York state. ''Cameroceras'' and ''Endoceras'' have even been applied to different stages of the same species. Although ''Cameroceras'' takes precedence where the two refer to the same species, its vague application leaves ''Endoceras'' or other better-described genus the term of choice.

Paleobiology

The lifestyle and habits of ''Cameroceras'' can only be surmised. They were almost certainly stalkers and ambush predators that moved across the sea floor or lay in wait. The large rigid shell would have made maneuvering difficult. The larger ones especially were probably not active swimmers. The very largest may have remained on the bottom without ever changing position. As with all endoceratids ''Cameroceras'' was weighted so as to be horizontally stable. This would have been achieved by the endocones in the apical portion of the siphuncle that would have compensated for the visceral mass forward in the body chamber. The endocones would also have sealed off the more apical chambers from the siphuncle limiting changes in ballast to the more forward, centrally located, chambers. The result is that changes in buoyancy would have had little effect on horizontal stability.

Description

Taxonomic usage

Paleobiology

See also

References

Further reading