''Gryponautilus'' is a genus of
Upper Triassic
The Late Triassic is the third and final epoch of the Triassic Period in the geologic time scale, spanning the time between Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch. T ...
nautilids (''generally coiled nautiloid cephalopods'') belonging to the
trigonoceratacean family
Grypoceratidae
Grypoceratidae is the longest-lived family of the Trigonoceratoidea, or of the near equivalent Centroceratina; members of the Nautilida from the Upper Paleozoic and Triassic.Kummel,B. 1964. Nautiloidea-Nautilida, Treatise on Invertebrate Paleont ...
, characterized by
involute
In mathematics, an involute (also known as an evolvent) is a particular type of curve that is dependent on another shape or curve. An involute of a curve is the Locus (mathematics), locus of a point on a piece of taut string as the string is eith ...
, inflated shells, which at maturity develop narrowly rounded keel-like
venters. Venters on inner whorls are truncated and broadly convex to concave.
Immature forms bear a resemblance to ''
Grypoceras''.
References
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Prehistoric nautiloid genera
{{paleo-nautiloidea-stub