Alibashinautilus ambiguus Korn & Ghaderi, 2025, gen. et sp. nov.

Alibashinautilus ambiguus gen. et sp. nov. urn:lsid:zoobank.org:act: 581650DC-6AA3-4D6E-9DA5-5409F4945D92 Fig. 28; Table 16 Diagnosis Species of Alibashinautilus gen. nov. with thinly discoidal, subevolute conch (ww/dm ~ 0.35; uw/dm ~0.35), weakly circular whorl profile (ww/wh ~1.00) and very high coiling rate (WER ~2.30) at a conch diameter of 120 mm. Whorl profile nearly circular with continuously rounded venter and flanks; whorl overlap very small. Ornament without ribs. Suture line with wide and very shallow external lobe and very shallow lateral lobe. Etymology From the Latin ‘ ambiguus ’ (adj.)= ‘questionable’; because of the unclear assignment of the species. Type material Holotype IRAN – East Azerbaijan • Ali Bashi 4; Paratirolites Limestone (1.50 m below top) of the Ali Bashi Formation (late Changhsingian); 2011; Korn et al. leg.; illustrated in Fig. 28; MB.C.32055. Description Holotype MB.C.32055 has a conch diameter of 120 mm and suffered from some corrosion (Fig. 28B). However, it allows the study of the conch shape and proportions across one volution. The whorl profile is nearly circular with a very small overlap upon the preceding volution (Fig. 28A). There is no sculpture visible; the conch appears to be smooth. Almost the entire specimen is chambered; the suture line is almost straight. Despite of corrosion, it is clear that there are no ribs or other sculpture. Remarks Alibashinautilus ambiguus gen. et sp. nov. is distinguished from A. vetus gen. et sp. nov. by the lack of ribs on the outer flank. Other differences are the narrower umbilicus (uw/dm ~ 0.37 in A. ambiguus, but ~ 0.50 in A. vetus) and the higher coiling rate (WER ~ 2.30 in A. ambiguus in contrast to ~ 1.85 in A. vetus).