''Galtoceras'' is a cyrtoconic nautiloid from the Middle Silurian of North America, named by Foerste in 1934. ''Galtoceras'' is genus of the

Oncocerida The Oncocerida comprise a diverse group of generally small nautiloid cephalopods known from the Middle Ordovician to the Mississippian (early Carboniferous; one possible member is known from the Early Permian), in which the connecting rings are t ...

and of the oncocerid family

Acleistoceratidae The Acleistoceratidae is a family of oncocerids that contains genera characterized by depressed (or rarely compressed) exogastric brevicones and cyrtocones (Sweet, 1964 K398) that range from the Middle Silurian to the Middle Devonian. The siphu ...

. As with the ascleistoceratids, the curvature is exogastric, such that the lower side, or venter, is on the outside curve. The shell is elongate and slender, wider than high, with a subventral, empty, cyrtochoanitic

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 ...

, with segments somewhat expanded into chambers but abruptly narrowed at septal openings. '' Euryrizoceras'' and '' Tumidoceas'' are similar genera, also included in the Acleistoceratidae, but which are less slender than ''Galtoceras''.

References

* Nautiloids Silurian cephalopods Silurian cephalopods of North America {{paleo-cephalopod-stub