''Blakeoceras'' is a

nautiloid Nautiloids are a group of cephalopods (Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and ''Allonautilus''. Fossil nautiloids are diverse and species rich, with over 2,500 recorded species. Th ...

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

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 with a curved shell that lived in shallow seas from the

Silurian The Silurian ( ) is a geologic period and system spanning 23.5 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 third and shortest period of t ...

to the

Middle Devonian In the geological timescale, the Middle Devonian epoch (from 393.3 ± 1.2 million years ago to 382.7 ± 1.6 million years ago) occurred during the Devonian period, after the end of the Emsian age. The Middle Devonian epoch is subdivided into two ...

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 The phragmocone is the chambered portion of the shell of a cephalopod. It is divided by septa into camerae. In most nautiloids and ammonoids, the phragmocone is a long, straight, curved, or coiled structure, in which the camerae are linked by ...

are short and wide, separated by straight, close spaced septa. Body chamber short.

Siphuncle The siphuncle is a strand of biological tissue, tissue passing longitudinally through the mollusc shell, shell of a cephalopod mollusc. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the li ...

ventro-marginal, with internal, radial actinosiphonate deposits and concave segments. ''Blakeocers'' is similar to '' Perimecoceras'' 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 '' Perimecoceras'' which has its origin in the Oncoceratidae, 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,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authore ...

, 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