''Solenochilus'', type genus of the

Solenochilidae Solenochilidae is a small family of Carboniferous and Early Permian nautilids, similar and related to the Aipoceratidae The Aipoceratidae are a small family of Carboniferous nautilids which have smooth shells and loosely coiled to faintly i ...

is an extinct cosmopotilian nautilid from the Lower Pennsylvanian to the Lower Permian with a rapidly expanding, coiled globular shell with few whorls, from which prominent spines extend laterally from the umbilical area at maturity. ''Solenochilus'' is derived from the Upper Mississippian '' Acanthonautilus'', principally through evolutionary changes in 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 ...

. The siphuncle in both ''Solenochilus'' and ''Acanthonautilus'' is ventral, running just inside the outer rim of the shell. In both the siphuncle is mostly composed of thin connecting rings. The siphuncle in ''Solenochilus'' is wider and has a more sinuous profile than that of ''Acanthonautilus''. Both swing dorsally between septa, but more so in ''Solenochilus''. In both the septal necks are somewhat long and straight on the ventral side but in ''Solenochilus'' they are cyrtochoanitic and recumbent on the dorsal side, rather than simply curved back, cyrtochoanitic. ''Solenochilus'' resembles its predecessor, ''Acanthonautilus, in overall anatomy, and both genera superficially resemble '' Permonautilus'' from the Clydonautilaceae.

References

* Kummel, B. 1964; Nautiloidea—Nautilida,

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, Nautiliodea; Geological Society of America and University of Kansas press {{Taxonbar, from=Q7557618 Nautiloids Pennsylvanian first appearances Cisuralian genus extinctions