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 Paratirolites quadratus Korn & Ghaderi in Korn et al. , 2016 Figs 38–39 ; Table 18 Paratirolites quadratus Korn & Ghaderi in Korn et al. , 2016: 866 , text-fig. 25. Diagnosis Paratirolites with conch reaching 90 mm dm. Subadult stage with trapezoidal, weakly depressed whorl profile (ww/wh =1.35–1.60) and broadly rounded venter; about 11–13 ribs ending in spiny ventrolateral nodes. Adult stage with weakly trapezoidal to nearly quadrate and weakly depressed whorl profile (ww/wh =1.00–1.20), weakly concave venter and angular ventrolateral shoulder; coarse and shallow ribs on flanks. Prongs of external lobe multiply serrated; altogether about 14–17 notches of E, A and L lobes. Material examined Holotype IRAN • 1 specimen ; East Azerbaijan , Ali Bashi N section ; Paratirolites Limestone , 1.70 m below the top; illustrated by Korn et al. (2016 : text-fig. 25); MB.C.25296 . Additional material IRAN • 3 specimens ; Esfahan Province , Baghuk Mountain C section ; Hambast Formation ; MB.C.29331 to MB.C.29333 . Description Specimen MB.C.29932 is a nicely preserved specimen of 72 mm conch diameter ( Fig. 38A ). It shows weak septal crowding at 48 mm diameter and thus half of the last volution belongs to the body chamber. The whorl profile shape changes from trapezoidal with convex flanks of the subadult stage to parallelsided at the beginning of the body chamber; at the same time the shape of the venter changes from weakly convex to nearly totally flattened. The sculpture of the subadult stage possesses 13 conical ventrolateral nods per volution; they originate from rounded radial ribs. On the body chamber the nodes are weaker and become radially elongated, they are connected with low, rounded dorsolateral ribs. The suture line of specimen MB.C.29932 shows an asymmetric external lobe with weakly concave flanks, of which both prongs are trifid. Also on the venter follows the very narrow, weakly inflated ventrolateral saddle and the asymmetric adventive lobe ( Fig. 38B ). Specimen MB.C.29933 is a larger specimen with 101 mm conch diameter ( Fig. 39A ). It shows similar conch and sculpture characteristics but differs from the preceding specimen in the coarser ventrolateral nods and the larger phragmocone ( 62 mm dm). Its suture line has a parallel-sided external lobe with parallel-sided trifid prongs. The ventrolateral saddle is very narrow and the adventive lobe shows strong serration by small notches, which climb up the ventral flank to more than half of the lobe depth. The lateral saddle is weakly inflated and lower than the ventrolateral saddle and the lateral lobe is nearly parallel-sided and possesses five small notches ( Fig. 39B ). Table 18. Conch dimensions (partly estimated) and ratios of selected specimens of Paratirolites quadratus Korn & Ghaderi in Korn et al. (2016) from Baghuk Mountain.

Specimen	dm	ww	wh	uw	ah	ww/dm	ww/wh	uw/dm	WER	IZR
MB.C.29933	101.0	26.8	32.6	43.3	31.5	0.27	0.82	0.43	2.11	0.03
MB.C.29933	70.4	28.5	24.4	28.2	–	0.40	1.17	0.40	–	–
MB.C.29932	71.5	23.6	25.4	30.4	23.9	0.33	0.93	0.43	2.26	0.06
MB.C.29932	47.9	26.3	15.7	20.5	–	0.55	1.68	0.43	–	–
MB.C.29931	61.1	21.5	19.6	26.4	18.4	0.35	1.10	0.43	2.05	0.06

Remarks Paratirolites quadratus differs from the other species of Paratirolites in the slightly trapezoidal, nearly quadrate whorl profile in the adult conch and the very long, spiny ventrolateral nodes. Fig. 38. Paratirolites quadratus Korn & Ghaderi, 2016 . A . Lateral and dorsal view, specimen MB.C.29932, section E, float. B . Suture line, specimen MB.C.29932, at 13.5 mm wh. Abbreviation: see Material and methods. Scale bar units =1 mm. Stratigraphic range At Baghuk Mountain only known from float from the upper part of the Hambast Formation; Stoyanowites dieneri Zone in the Julfa region .