The Clydonautilidae are Middle and Upper Triassic nautiloid cephalopods, which are derivatives of the clydonautiloidean family Liroceratidae, that have generally smooth, involute, globular to compressed shells, characterized by a suture with prominent lobes and saddles.

The family is known to contain five genera, These are: Of these only Styrionautilus is known from the Middle Triassic.

The five genera in the Clydonautilidae form a sequence of increasing sutural complexity, beginning with Styrionautilus and ending with Clydonautilus.

Styrionautilis, which has the simplest suture of the five, has a broad ventral saddle with a flat bottom and a gently curved lateral lobe.

Clydonauatilus at the opposite extreme has a secondary ventral saddle within the ventral lobe modifying the primary ventral saddle and a deep, asymmetric lateral lobe.