The Changhsingian (Late Permian) ammonoids from Baghuk Mountain (Central Iran) Author Korn, Dieter 286CA4F3-7EBC-4AEF-A66A-B2508D001367 Museum für Naturkunde, Leibniz Institut for Research on Evolution and Biodiversity, Invalidenstrasse 43, 10115 Berlin, Germany. dieter.korn@mfn.berlin Author Hairapetian, Vachik 1AB10F8F-4576-481B-9270-5DCD25110DBB Department of Geology, Esfahan (Khorasgan) Branch, Islamic Azad University, Esfahan, Iran. vhairap@gmail.com Author Ghaderi, Abbas 925F2B42-7326-4461-B2A6-83CB83ECCC63 Department of Geology, Faculty of Science, Ferdowsi University of Mashhad, Azadi Square, 9177948974, Mashhad, Iran. aghaderi@um.ac.ir Author Leda, Lucyna 81481AFA-C8EE-4E90-A954-FD0E7987621E Museum für Naturkunde, Leibniz Institut for Research on Evolution and Biodiversity, Invalidenstrasse 43, 10115 Berlin, Germany. lucyna.skorpion3@wp.pl Author Schobben, Martin 44C2A45A-B16C-434F-8F22-FC9C0FCA2551 Utrecht University, Department of Earth Sciences, Princetonlaan 8 A, 3584 CB Utrecht, The Netherlands. & Department of Geology, Esfahan (Khorasgan) Branch, Islamic Azad University, Esfahan, Iran. schobbenmartin@gmail.com Author Akbari, Amir 3C9DB6F9-2034-418F-876C-49359D07D29F Department of Geology, Esfahan (Khorasgan) Branch, Islamic Azad University, Esfahan, Iran amakbari80@yahoo.com text European Journal of Taxonomy 2021 2021-10-27 776 1 106 journal article 3782 10.5852/ejt.2021.776.1559 453c885c-f427-4a38-ab97-dc14b686e126 2118-9773 5604715 226B6C59-8620-4A29-9BEF-359BE67A1A2C Arasella falcata Korn & Hairapetian sp. nov. urn:lsid:zoobank.org:act: B2DA940A-842C-452B-8906-A29E07291FFE Fig. 21 ; Table 6 Diagnosis Species of Arasella with conch reaching 35 mm dm. Subadult and adult stage with compressed whorl profile (ww/wh=0.60–0.70) and rounded venter; 25 curved ribs which are coarsest on the inner flanks. Etymology From the Latin ‘ falx ’, meaning ‘sickle’, because of the rib course. Material examined Holotype IRAN • Esfahan Province , Baghuk Mountain C section ; Hambast Formation , 0.05 m below top; illustrated in Fig. 21A ; MB.C.29734 . Paratypes IRAN • 1 specimen ; Esfahan Province , Baghuk Mountain 1 section ; Hambast Formation ; MB.C.29733 • 1 specimen ; Esfahan Province , Baghuk Mountain G section ; Hambast Formation ; MB.C.29735 • Fig. 21. Arasella falcata Korn & Hairapetian sp. nov. A . Lateral and dorsal view, holotype MB.C.29734, section C, -0.05 m. B . Lateral view, paratype MB.C.29733, section 1, -0.05 m. C . Lateral views, paratype MB.C.29736, section H, -0.05 m. Scale bar units =1 mm. Table 6. Conch dimensions (partly estimated) and ratios of selected specimens of Arasella falcata Korn & Hairapetian sp. nov. from Baghuk Mountain.

Specimen	dm	ww	wh	uw	ah	ww/dm	ww/wh	uw/dm	WER	IZR
MB.C.29734	25.1	5.1	8.1	10.4	7.1	0.20	0.63	0.41	1.94	0.12
MB.C.29734	18.0	3.6	5.8	7.7	–	0.20	0.62	0.43	–	–

1 specimen ; Esfahan Province , Baghuk Mountain H section ; Hambast Formation ; MB.C.29736 • 1 specimen ; Esfahan Province , Baghuk Mountain ; Hambast Formation ; MB.C.29737 . Description Holotype MB.C.29734 is a somewhat corroded specimen with a conch diameter of 24 mm ( Fig. 21A ). It is extremely discoidal (ww/dm =0.20) and subevolute (uw/dm =0.43) with a compressed whorl profile (ww/wh =0.63). The flanks are nearly parallel and the venter is rounded. The last volution shows about 25 ribs, which are sharpest and coarsest on the inner flank; they turn slightly forward and become weaker on the outer flank to diminish. Remarks Arasella minuta shows much coarser ribs, particularly on the outer flanks, while A. falcata sp. nov. possesses a much weaker sculpture with ribs strongest in in dorsolateral area. Stratigraphic range Topmost part of the Hambast Formation; immediately below the extinction horizon ( Arasella minuta Zone ).