Subclymenioidea Shimansky, 1962

Superfamily Subclymenioidea Shimansky, 1962

Diagnosis

Superfamily of the suborder Domatoceratina subordo nov. with discoidal, subinvolute to evolute conch. Whorl profile often subquadrate to polygonal, usually with distinct ventrolateral shoulder and distinct umbilical margin. Derived species show a variation of modifications including a concave or acute venter or an angular or skid-like ventrolateral shoulder. Whorl overlap extremely small to moderate. Sculpture in most species lacking. Septa simply domed but with ventral inflexion in derived species. Suture line usually depending on the whorl profile, with shallow to deep external lobe.

Included families

Apheleceratidae Hyatt, 1893 [nomen nullum].

Subclymeniidae Shimansky, 1962 (Early to Late Carboniferous; 6 genera, 59 species).

Phacoceratidae Shimansky, 1962 (Early to Late Carboniferous; 6 genera, 13 species). Aphelaeceratidae Shimansky, 1962 [synonym of Subclymeniidae ].

Epistroboceratidae fam. nov. (Early to Late Carboniferous; 4 genera, 36 species).

Remarks

The superfamily Subclymenioidea shows a wide range of conch morphologies and sculptures and is therefore difficult to define on the basis of adult morphology. The reason for this is a rapid morphological evolution during the Late Tournaisian and Early Viséan, which produced a high diversity of conch shapes and sculptures known from only a few other clades of nautilids. The common feature of all species is the shape of the whorl profile in the juvenile stage, characterised by sharp longitudinal ridges on a raised umbilical margin.

Three evolutionary lineages can be assumed to form the superfamily Subclymenioidea :

Epistroboceratidae fam. nov. – Forms that retained the polygonal shaped whorl profile once acquired; the whorl profile became more and more compressed during evolution. Whorl profile variable, usually polygonal, sculpture with few very coarse longitudinal ridges of different strength ( Fig. 15 View Fig ).

Subclymeniidae Shimansky, 1962 . – Forms that developed a flattened or more or less deeply concave venter. Suture line with rather deep external lobe that was caused by a septal inflexion ( Fig. 16 View Fig ).

Phacoceratidae Shimansky, 1962 . – Forms that developed an extremely compressed whorl profile with a sharp venter ( Fig. 17 View Fig ).