Ocunautilidae, Korn & Hairapetian, 2025

Family Ocunautilidae fam. nov.

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New family – Korn 2025: 65, 69, fig. 42. — Korn & Ghaderi 2025: 25.

Type genus

Ocunautilus gen. nov.

Diagnosis

Family of the superfamily Grypoceratoidea with a usually discoidal, subinvolute conch. Whorl profile in the adult stage weakly compressed or weakly depressed; flanks and venter usually separated by a distinct ventrolateral shoulder, venter more or less concave. Umbilical margin usually subangular or angular, rarely rounded; umbilical wall steep, often flattened. Ornament usually consisting of fine growth lines. Septum simple in shape, concavely domed; suture line depending on whorl profile with shallow to V-shaped external lobe and shallow lateral lobe.

Etymology

Named after the type genus Ocunautilus gen. nov.

Included genera

Pseudotitanoceras Shimansky, 1965 (Permian); Azarinautilus Korn & Ghaderi, 2025 (Permian); Ocunautilus gen. nov. (Permian); Aifinautilus gen. nov. (Permian).

Remarks

Grypoceratids with a whorl profile characterised by a concave venter, a pronounced ventrolateral shoulder with skid-like extensions, strongly convergent flanks and an angular umbilical margin occurred iteratively in the Late Carboniferous and the Late Permian. It is not clear whether they are phylogenetically related with each other or belong to independent evolutionary lineages.

The Late Permian forms are morphologically closely related; they are characterised by an ontogenetically rather late transformation of the juvenile growth stage with rounded or flattened venter into the adult stage with concave venter. Furthermore, the Late Permian forms have rather stout conchs (ww/dm between 0.40 and 0.55), whereas the conchs of the Late Carboniferous forms are usually more slender. The umbilical margin is more pronounced in the Late Permian genera. These are probably good reasons to assume that the Late Permian forms evolved independently of the Late Carboniferous forms and not represent a long-ranging evolutionary lineage.

The family Ocunautilidae fam. nov. is characterised by a transformation of the originally broadly rounded venter into a more or less concave venter in the middle ontogenetic stage. The new family can therefore easily be derived from the family Domatoceratidae , some species of which also show a similar transformation. In addition to the modification of the venter, some members of the family Ocunautilidae show a narrowing of the umbilicus and a subangular or angular shape of the umbilical margin.