Tardunautilus Korn & Ghaderi, 2025, gen. nov.

Genus Tardunautilus gen. nov. urn:lsid:zoobank.org:act: A29DB483-82CF-4C67-AC41-D6FBE9C79244 New genus E – Korn 2025: 56. Type species Tardunautilus nimius gen. et sp. nov. Diagnosis Genus of the family Foordiceratidae with evolute conch; whorl profile rounded triangular or rounded trapezoidal, depressed with broadly rounded venter. Sculpture with one or two rows of conical ribs near the ventrolateral shoulder. Suture line with very shallow external lobe and broadly rounded lateral lobe; without annular process. Etymology From the Latin ‘ tardus ’ (adj., m.) =‘slow’; because of the low coiling rate of the conch, and ‘ nautilus ’ because of the relationship. Included species NW Iran (this paper): Tardunautilus nimius gen. et sp. nov., Wuchiapingian; Tardunautilus minor gen. et sp. nov., Wuchiapingian. Central Iran (Korn & Hairapetian in press): new species J to be described by Korn & Hairapetian (in press), Wuchiapingian. Remarks The new genus can be easily distinguished from all other genera in the assemblage of Julfa because of its combination of a conch shape with a wide umbilicus, a rounded triangular or rounded trapezoidal whorl profile and a sculpture consisting of conical nodes. A genus with a similar morphology is Pseudotemnocheilus, but this is mostly known from much smaller specimens of about 40–60 mm in diameter. These smaller specimens have a much narrower umbilicus (uw/dm ~ 0.40) compared to Tardunautilus gen. nov. (uw/dm ~ 0.47) and a less depressed whorl profile (ww/wh ~ 1.30) than Tardunautilus (ww/wh ~1.40–1.80). The coiling rate is much lower in Tardunautilus (WER below 2.00) when compared to Pseudotemnocheilus (WER greater than 2.25).