Aifinautilus Korn & Hairapetian, 2025, gen. nov.

Genus Aifinautilus gen. nov. urn:lsid:zoobank.org:act: C251419E-4EF4-4D59-BBAA-FEEA876287CC New genus B – Korn 2025: 43. — Korn & Ghaderi 2025: 30. Type species Aifinautilus icanus gen. et sp. nov. Diagnosis Genus of the family Ocunautilidae fam. nov. with a subinvolute conch. High coiling rate; whorl profile rounded rectangular, weakly depressed with concave venter. Without sculpture. Suture line with shallow external lobe and broadly rounded lateral lobe; without annular process. Etymology From the Greek ‘αἴφνης’= ‘suddenly, unexpected’; because of the unexpected conch form of a Permian nautiloid. Included species NW Iran (Korn & Ghaderi 2025): Aifinautilus hebes Korn & Ghaderi, 2025, Wuchiapingian. Central Iran (this paper): Aifinautilus icanus gen. et sp. nov., Wuchiapingian. Remarks Aifinautilus gen. nov. is difficult to confuse with any other genus of Palaeozoic nautiloids because of its peculiar conch morphology with the box-shaped whorl profile, the concave venter, the skid-like ventrolateral shoulder, parallel flanks and flattened umbilical wall. Ocunautilus gen. nov. differs from Aifinautilus by its clearly convergent flanks, resulting in a much narrower venter; it has an angular ventrolateral shoulder and an angular umbilical margin. Pseudotitanoceras also has convergent flanks and is characterised by a row of nodes on the ventrolateral shoulder and sometimes also at the umbilical margin (Shimansky 1965: 163). The conch of Aifinautilus gen. nov. is very similar to that of some species of the Triassic genus Germanonautilus Mojsisovics, 1902 (e.g., Mojsisovics 1902; Dzik 1984; Sobolev 1989). The main difference between the two genera is the presence of an annular lobe in Germanonautilus, which is absent in Aifinautilus. The siphuncle has a more dorsal position in Germanonautilus. The Late Carboniferous genus Titanoceras has a superficially similar conch shape with a concave venter and almost parallel flanks. However, the conch of Titanoceras has almost non-overlapping whorls and the sculpture is characterised by ventrolateral tubercles. Shimansky (1965: 163) has already suggested that the Late Carboniferous (Titanoceras) and Late Permian forms (Pseudotitanoceras) belong to two independent, homoeomorphic evolutionary lineages and that both arose from Domatoceras.