Permoceras, the sole member of the Permoceratidae, is a coiled nautiloid with a smooth, compressed involute shell, whorls highter than wide, earlier whorls hidden from view. The venter is rounded as are the ventral and umbilical shoulders, the flanks flattened. The siphuncle

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 Spirula...

 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

Nautilida

The Nautilida constitute a large and diverse order of generally coiled nautiloid cephalopods that began in the mid Paleozoic and continues to the present with a single family, the Nautilidae which includes two genera, Nautilus and Allonautilus, with six species...

 superfamily, Trigonocerataceae, and is derived from the Mississippian (L Carb) - Triassic

Triassic

The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

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

Timur

Timur , historically known as Tamerlane in English , was a 14th-century conqueror of West, South and Central Asia, and the founder of the Timurid dynasty in Central Asia, and great-great-grandfather of Babur, the founder of the Mughal Dynasty, which survived as the Mughal Empire in India until...

 in the East Indies and named by Miller and Collinson in 1953

Permoceras almost precisely resembles Pseudonautilus from the Upper Jurassic.