''Permoceras'', the sole member of the family Permoceratidae, is a genus of coiled

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 ...

s with a smooth, compressed involute shell, whorls higher than wide, earlier whorls hidden from view. The venter is rounded as are the ventral and umbilical shoulders, the flanks flattened. The

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 ...

is ventrally subcentral. The suture, which is most characteristic, has a deep, narrow pointed ventral lobe and large, asymmetrical pointed lobes on either side. ''Permoceras'' is included in the nautilid superfamily, Trigonocerataceae, and is derived from the

Mississippian Mississippian may refer to: * Mississippian (geology), a subperiod of the Carboniferous period in the geologic timescale, roughly 360 to 325 million years ago * Mississippian cultures, a network of precontact cultures across the midwest and Easte ...

(L Carb) -

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

Grypoceratidae. ''Permoceras'' was first identified in the Lower Permian of

Timur Timur, also known as Tamerlane (1320s17/18 February 1405), was a Turco-Mongol conqueror who founded the Timurid Empire in and around modern-day Afghanistan, Iran, and Central Asia, becoming the first ruler of the Timurid dynasty. An undefeat ...

in the East Indies and named by Miller and Collinson in 1953 The coiling and whorl structure of ''Permoceras'' almost precisely resembles those of '' Pseudonautilus'' from the Upper Jurassic.

References

* 1964; Nautiloidea-Nautilida,

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 Nautiliodea, Geological Society of America and University of Kansas press * Sepkoski, J.J. Jr. 2002. A compendium of fossil marine animal genera. D.J. Jablonski & M.L. Foote (eds.). ''Bulletins of American Paleontology'' 363: 1–560
Sepkoski's Online Genus Database (CEPHALOPODA)
Prehistoric nautiloid genera {{paleo-Nautiloidea-stub

See also

References