Paranautilus is a genus of the Nautiloid family Liroceratidae with a very involute, moderately globular, smooth shell. The venter, at the outer rim, is arched, grading into broadly convex flanks. The dorsom, on the inner rim, is deeply impressed. Septa a close spaced, with slightly sinuous sutures. A member of the Clydonautilaceae

Clydonautilaceae

The Clydonautilaceae is a superfamily within the nautiloid order Nautilida characterized by smooth, generally globular, shells with nearly straight sutures, in early forms but developing highly differentiated sutures in some later forms...

, Paranautilus lived during the Middle and Late Triassic (Anisian

Anisian

In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from 245 million years ago until 237 million years ago, approximately...

 - Norian

Norian

The Norian is a division of the Triassic geological period. It has the rank of an age or stage . The Norian lasted from 216.5 ± 2.0 to 203.6 ± 1.5 million years ago. It was preceded by the Carnian and succeeded by the Rhaetian.-Stratigraphic definitions:The Norian was named after the Noric Alps in...

) in what is now North America, Europe, and south Asia. Contemporary Liroceratids

Liroceratidae

Liroceratidae is an extinct family of nautilids, shelled marine molluscs, belonging to the Clydonautilaceae, consisting of generally smooth, involute, nautiliconic forms with a small umbilicus...

 include Indonautilus and Sibyllonautilus.