What is "gryponautilus"

Gryponautilus is an Upper Triassic nautilid (generally coiled nautiloid cephalopods) belonging to the trigonoceratacean family Grypoceratidae, characterized by involute, 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.