Shahrezanautilus weyeri, Korn & Hairapetian, 2025

Shahrezanautilus weyeri gen. et sp. nov.

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Fig. 30 View Fig ; Table 23 View Table 23

Diagnosis

Species of Shahrezanautilus gen. nov. with a thinly pachyconic, subinvolute conch (ww/dm ~ 0.70; uw/dm ~0.25), weakly depressed whorl profile (ww/wh ~1.40) and extraordinarily high coiling rate (WER ~ 3.40) at a conch diameter of 60 mm. Whorl profile with a weakly convex venter, a pronounced ventrolateral shoulder, flatly convex and weakly convergent flanks, a subangular umbilical margin, a steep and flattened umbilical wall and a small imprint zone ( IZR ~ 0.10). Suture line with a broadly rounded and shallow external lobe and a broadly rounded lateral lobe.

Etymology

Named after Dieter Weyer ( Berlin), who collected the holotype of the new species.

Type material

Holotype

IRAN – Esfahan Province • Shahreza; Hambast Formation , Vedioceras beds ( late Wuchiapingian); 2002; D. Weyer leg.; illustrated in Fig. 30 View Fig ; MB.C.32148 .

Paratype

IRAN – Esfahan Province • 1 specimen; Baghuk Mountain ; Hambast Formation, Vedioceras beds ( late Wuchiapingian); 2011; Korn et al. leg.; MB.C.32149 .

Description

Holotype MB.C.32148 is an incomplete, fully chambered specimen with a phragmocone diameter of at least 75 mm ( Fig. 30A View Fig ). It has been preserved without remains of the shell. The conch is, at 57 mm diameter, thinly pachyconic and subinvolute (ww/dm= 0.68; uw/dm = 0.26) with and extraordinarily high coiling rate (WER= 3.38) and a small whorl overlap zone ( IZR =0.07). The whorl profile is weakly depressed (ww/wh = 1.39) with a convex venter, a slightly pronounced by rounded ventrolateral shoulder and slightly flattened convergent flanks. The umbilical margin is very distinctive and subangular; it delimitates the broad and nearly flat, almost perpendicular umbilical wall ( Fig. 30B View Fig ). The suture line shows a shallow and broadly rounded external lobe and a twice as wide and deep, broadly rounded lateral lobe ( Fig. 30C View Fig ). The last volution of the phragmocone has slightly more than 20 septa (CLI =18) and thus some indication for terminal septal crowding.

Remarks

Shahrezanautilus weyeri gen. et sp. nov. differs from S. ghaderii gen. et sp. nov. in having a much wider umbilicus; the uw/dm ratio is about 0.25 in S. weyeri gen. et sp. nov. but only about 0.15 in S. ghaderii . This difference parallels a difference in the whorl overlap rate, which is only about 0.07 in S. weyeri , but 0.25 in S. ghaderii and in the coiling rate, which is higher in S. weyeri (WER ~3.40 compared to about 3.10 in S. ghaderii ).

Shahrezanautilus weyeri gen. et sp. nov. is difficult to confuse with any other Late Permian nautiloid species due to its specific morphology with a very high, flattened umbilical wall and an angular umbilical margin. The two species Julfanautilus hairapetiani Korn & Ghaderi, 2025 and especially J. ashourii Korn & Ghaderi, 2025 show a slight similarity, although they have a concave venter.