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 serus Korn & Ghaderi in Korn et al. , 2016 Fig. 40 ; Table 19 Paratirolites serus Korn & Ghaderi in Korn et al. , 2016: 868 , text-fig. 27. Diagnosis Paratirolites with conch reaching 80 mm dm. Subadult stage with weakly to strongly trapezoidal, depressed whorl profile (ww/wh =1.40–1.80) and broadly rounded venter; 12–14 coarse conical ventrolateral nodes. Adult stage with circular or slightly trapezoidal, weakly to moderately depressed whorl profile (ww/wh =1.20–1.60), flattened venter and subangular to angular ventrolateral shoulder; numerous ribs on the flank. Prongs of external lobe simple; altogether 6–9 notches of E, A and L lobes. Material examined Holotype IRAN • East Azerbaijan , Ali Bashi N section ; Paratirolites Limestone , 0.65 m below the top; illustrated by Korn & Ghaderi in Korn et al. (2016 : text-fig. 27a); MB.C.25300 . Additional material IRAN • 1 specimen ; Esfahan Province , Baghuk Mountain C section ; Hambast Formation ; MB.C.29934 • 2 specimens ; Esfahan Province , Baghuk Mountain E section ; Hambast Formation ; MB.C.29935 to MB.C.29936 • 1 specimen ; Esfahan Province , Baghuk Mountain F section ; Hambast Formation ; MB.C.29937 . Description Specimen MB.C.29936 has 62 mm conch diameter and is the largest available specimen ( Fig. 40A ). It is corroded but still rather well preserved and allows the study of three whorls. A little more than half a volution belongs to the body chamber. The weakly depressed whorl profile (ww/wh = 1.05) of the body chamber is trapezoidal with weakly diverging flanks and the flattened venter is separated from the flanks by a subangular ventrolateral shoulder. The sculpture changes, on the last portion of the phragmocone, from a subadult stage with 14 coarse ventrolateral nodes per volution to the adult stage with numerous weak radial ribs with weak ventrolateral nodes on the flank. Fig. 40. Paratirolites serus Korn & Ghaderi, 2016 . A . Lateral and dorsal view, specimen MB.C.29936, section E, float. B . Lateral and dorsal view, specimen MB.C.29934, section C, -0.60 m. C . Lateral and dorsal view, specimen MB.C.29937, section F, -0.75 m. D . Suture line, specimen MB.C.29934, at 16.0 mm ww, 10.3 mm wh. E . Whorl profile proportions. Abbreviations: see Material and methods. Scale bar units= 1 mm. Table 19. Conch dimensions (partly estimated) and ratios of selected specimens of Paratirolites serus 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.29936	61.8	21.3	20.5	26.2	19.7	0.34	1.04	0.42	2.15	0.04
MB.C.29934	46.7	16.9	16.2	20.2	15.2	0.36	1.04	0.43	2.20	0.06
MB.C.29937	37.8	16.9	12.8	15.7	12.0	0.45	1.32	0.42	2.15	0.06
MB.C.29935	36.7	14.7	13.6	15.0	12.7	0.40	1.08	0.41	2.34	0.07

Specimen MB.C.29934 is a smaller individual with 48 mm conch diameter and is better preserved than the preceding one with half a volution of the body chamber preserved ( Fig. 40B ). It shows a weakly trapezoidal, weakly depressed body chamber whorl profile (ww/wh=1.05) with rounded ventrolateral shoulder and a broadly rounded venter, while the phragmocone has a more depressed whorl profile (ww/ wh= 1.40). The sculpture in the subadult stage has twelve coarse ventrolateral nodes, which become weaker and radially elongated on the body chamber, where they finally disappear and instead shallow radial dorsolateral ribs take place. The suture line of specimen MB.C.29934 has an external lobe with nearly parallel flanks and unserrated, narrow lanceolate prongs. The ventrolateral saddle is weakly asymmetric and the adventive lobe is strongly asymmetric with a steep ventral flank, four little notches and an oblique dorsal side. The lateral lobe possesses only three small notches ( Fig. 40D ). Remarks Paratirolites serus is the stratigraphically youngest species of the genus in the Baghuk Mountain sections. It differs from the other by its small conch size and the simple suture line with unsubdivided prongs of the external lobe. Subadult specimens of P. serus resemble some stratigraphically older species such as P. kittli and particularly P. vediensis . Paratirolites serus differs from these in the smaller conch diameter ( 40 mm maximum phragmocone diameter in contrast to 70–80 mm in P. kittli and P. vediensis ) and a simpler suture line with unsubdivided prongs of the external lobe. Stratigraphic range Upper part of the Hambast Formation; 0.75 to 0.60 m below the extinction horizon ( Abichites stoyanowi Zone ).