Grypoceratoidea Hyatt, 1900

Superfamily Grypoceratoidea Hyatt, 1900

Diagnosis

Superfamily of the suborder Domatoceratina subordo nov. with a discoidal, subinvolute to evolute conch. Whorl profile usually inverted trapezoidal with a distinct ventrolateral shoulder and a distinct umbilical margin. Derived species show a variation of modifications including a concave venter, a skid-like ventrolateral shoulder and an angular umbilical margin. Whorl overlap extremely small to moderate. Sculpture in most species lacking, in some species with short lateral ribs or ventrolateral nodes. Septa simply domed; suture line strongly dependent on the whorl profile, usually with broadly rounded lobes and narrowly rounded or subangular saddles.

Included families

Grypoceratidae Hyatt, 1900 (Early to Late Triassic).

Domatoceratidae Miller & Youngquist, 1949 (Early Carboniferous to Late Permian; 15 genera, 73 species).

Stenopoceratidae fam. nov. (Early to Middle Permian; 3 genera, 11 species).

New family to be described by Korn & Hairapetian (in press) (Late Permian; 4 genera, 7 species).

Remarks

Grypoceras Hyatt, 1883 , Domatoceras and related genera are characterised by more or less flattened flanks, which are bordered by distinct margins against the venter and the umbilical wall ( Fig. 18 View Fig ). Usually, the ventrolateral shoulder is more strongly pronounced than the umbilical margin, being subangular, angular or even raised to form skid-like extensions. A whorl profile with both a pronounced umbilical margin and also a pronounced ventrolateral shoulder is already present in the juvenile conch, i.e., at the end of the first whorl. In this respect, Domatoceras and related genera are similar to the metacoceratids. It is worth considering whether these two groups are closely related.

Three Carboniferous and Permian families, which represent evolutionary lineages, can be assigned to the superfamily Grypoceratoidea :

Domatoceratidae Miller & Youngquist, 1949 . – Forms that retained usually inverted trapezoidal whorl profile throughout their evolutionary history ( Fig. 19 View Fig ).

Stenopoceratidae fam. nov. – Forms that developed a very narrow venter in their evolutionary history ( Fig. 20 View Fig ).

New family to be described by Korn & Hairapetian (in press). – Forms that developed a concave venter, partly separated from a skid-like ventrolateral shoulder, in their evolutionary history ( Fig. 21 View Fig ).