Tardunautilus Korn & Ghaderi 2025

Genus Tardunautilus Korn & Ghaderi, 2025 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 (from Korn & Ghaderi 2025). Type species Tardunautilus nimius Korn & Ghaderi, 2025; by original designation. Included species NW Iran (Korn & Ghaderi 2025): Tardunautilus nimius Korn & Ghaderi, 2025, Wuchiapingian; Tardunautilus minor Korn & Ghaderi, 2025, Wuchiapingian. Central Iran (this paper): Tardunautilus aperimos sp. nov., Wuchiapingian. Remarks The new genus can be easily distinguished from all other genera in the assemblage from Baghuk Mountain 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 (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).