''Blakeoceras'' is a nautiloid

cephalopod A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head ...

from 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 ...

family

Nothoceratidae Nothoceratidae is a family of nautiloid cephalopods in the orthoceratoid order Oncocerida in which shells are exogastrically or endogastrically breviconic, planospiral, or torticonic; often with a constricted or visored aperture; and a siphun ...

with a curved shell that lived in shallow seas from the

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

to the Middle Devonian in what has become Europe. The shell of ''Blakeoceras'' is moderately curved (cyrtoconic) with the ventral side on the outer curvature (exogastric) Chambers in the phragmocone are short and wide, separated by straight, close spaced septa. Body chamber short.

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 ...

ventro-marginal, with internal, radial actinosiphonate deposits and concave segments. ''Blakeocers'' is similar to ''

Perimecoceras ''Perimecoceras'' is a genus of nothoceratids, nautilitoids in the order Oncocerida, with a slowly expanding, compressed, cyrtoconic shell, known from the Upper Silurian of central Europe. ''Perimecoceras'' is similar in general form to the onc ...

'' in general form but is more broadly expanded and has a proportionally shorter body chamber. '' Conostichoceras'' is less strongly curved and widens more laterally. '' Turnoceras'' is more strongly curved and has a much greater expansion. ''Conostichoceras'' and ''Turnoceras'' are also more breviconic (shorter). ''Blakeoceras'' is an early nothoceratid possibly derived from ''

'' which has its origin in the

Oncoceratidae Oncoceratidae is a family of nauatiloid cephalopods in the order Oncocerida established by Hyatt, 1884, that range from the Middle Ordovician to the Upper Silurian. Diagnosis Oncoceratidae are characterized by generally compressed, cyrtocon ...

, and is the likely source for the other exogastric nothoceratids with more greatly expanded shells. ''Blakeoceras'' was probably a bottom-feeder, based on its shell, that spent time, prowling, head down, over the sea floor.

References

*Sweet, W.C. 1964; Nautiloidea -Oncocerida;

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology'' (or ''TIP'') published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and co ...

, Part K; Geological Society of America and University of Kansas press; Teichert and Moore (eds)
''Blakeoceras''-Paleodb
{{Taxonbar, from=Q4924626 Oncocerida Silurian first appearances Middle Devonian genus extinctions Paleozoic life of Manitoba Prehistoric nautiloid genera