The Grypoceratidae begin with
Epidomatodceras from the
Lower Carboniferous (Mississippian), an evolute form with a smooth shell, subquadrate whorl section, and a sharp angular ventral lobe in the suture.
Epidomatoceras is followed by
Domatoceras,
Paradomatoceras,
Stearoceras,
Stenopoceras, and
Titanoceras from the
Upper Carboniferous (Pennsylvanian) and
Lower Permian.
Domatoceras,
Paradomatoceras, and
Titanoceras are rather similar in that they are somewhat large, evolute with whorls in contact but not deeply impressed along the inner margin of the whorls, and with straight flanks and flattened venters. Whorl sections vary from strongly compressed side to side with height much greater than width in
Paradomatoceras to slightly depressed with height less than width in
Titanoceras, with
Domatoceras subquadrate in between.
Stearoceras is involute with a depressed subtrapizoidal whorl section and slight ventral and lateral lobes.
Stenoporceras is subdiscoidal, flattened laterally, and has a suture with broad lateral lobes and a deep ventral saddle as found in
syringonautilids.
Permian genera include
Parastenopoceras, a smooth, involute form with a
semiellptical whorl section and ventral saddle;
Plummeroceras, a form similar to
Domatoceras but more evolute and with a deep ventral lobe;
Pselioceras, a smooth evolute form with a perforate
umbilicus, ovoid whorl section, and suture crossing straight over the venter; and
Virgaloceras, also similar to
Domatoceras but with a row of nodes on the umbilical wall and a ventral saddle instead of the ventral lobe in the suture.
Parastenopoceras,
Plummeroceras, and
Pselioceras are from the Lower Permian;
Virgaloceras is from the
Upper Permian. The last three genera are from the
Triassic, none having crossed from the Permian.
Grypoceras, given simply a Triassic, is like
Domatoceras but tending to be more involute and to have more rounded ventral shoulders.
Menuthionautilus from the
Lower Triassic has a rapidly expanding, smooth involute shell with a deep dorsal impression, broadly convex flanks and rounded venter, suture with a shallow ventral lobe and
siphuncle positioned against the venter.
Gryponautilus from the
Upper Triassic is broadly involute with a narrowly rounded, keel-like venter at maturity and shallow ventral and lateral lobes in the suture. All members of the Grypoceratidae have a ventral lobe with the exception of
Stenoporceras,
Parastenopoceras, and
Virgaloceras, which have a ventral saddle instead. The derivation of these three within the Grypoceratidae is uncertain.
Stenopoceras or
Parastenopoceras is the likely ancestor of the Syringonautilidae from the Triassic. ==Comparison of taxonomies==