''Metacoceras'' is a nautilitoid cephalopod from the Upper

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

(

Pennsylvanian Pennsylvanian may refer to: * A person or thing from Pennsylvania * Pennsylvanian (geology) The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, in the International Commission on Stratigraphy, ICS geologic timesca ...

) and

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...

, the shell of which is moderately evolute with a subquadrate whorl section, bearing nodes on the ventral or umbilical shoulders or both, but otherwise smooth. The

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 ...

is small, subcentral and orthochoanitic. The suture has shallow ventral and lateral lobes but no dorsal or annular lobe. ''Matacoceras'', named by Hyatt, 1883, is a genus in the nautilid superfamily Tainocerataceae. Its distribution is cosmopolitan. ''Aulametacoceras'', also a tainoceratid genus, is like ''Metacoceras except for having several longitudinal ridges and grooves along the venter. It is also a later genus with a more limited distribution, found in the Lower Permian and Upper Triassic in North America (U.S.A) and Europe (Alps). ''Mojvaroceras'' is a tainoderatid genus, like ''Metacoceras'' and its direct evolutionary descendant, differing in being slightly more involute and having a lobe on the inner, dorsal, side. It is known from Triassic sediments in Eurasia and western North America.

''References''

External links

*Bernhard Kummel, 1964. Nautiloidea-Nautilida. Treatise on Invertebrate Paleontology, Part K. Geological Soc. of America and University of Kansas press. Teichert and Moore (eds) {{Taxonbar, from=Q6822422 Nautiloids Pennsylvanian first appearances Permian genus extinctions