Clivotirolites decoratus Korn & Hairapetian, 2021

Korn, Dieter, Hairapetian, Vachik, Ghaderi, Abbas, Leda, Lucyna, Schobben, Martin & Akbari, Amir, 2021, The Changhsingian (Late Permian) ammonoids from Baghuk Mountain (Central Iran), European Journal of Taxonomy 776, pp. 1-106 : 62-64

Clivotirolites decoratus Korn & Hairapetian gen. et sp. nov.

urn:lsid:zoobank.org:act:0A7C7606-6D92-4630-BAF3-1A8E30B6486D

Figs 41–43 ; Table 20

Diagnosis

Species of Clivotirolites gen. nov. with conch reaching 110 mm dm. Subadult stage with trapezoidal, weakly depressed whorl profile (ww/wh=1.10–1.20) and slightly flattened venter; about 20–24 weak ventrolateral spines per volution. Adult stage with parallel or weakly diverging flanks and weakly compressed whorl profile (ww/wh =0.70–0.80), flattened, slightly tectiform venter and angular ventrolateral shoulder; numerous rounded ribs on flank ending in sharp ventrolateral nodes. Prongs of external lobe variable, simple to digitate; altogether 10–17 notches of E, A and L lobes.

Etymology

From the Latin ‘ decoratus ’, meaning ‘decorated’, because of the sculpture.

Material examined

Holotype IRAN • Esfahan Province, Baghuk Mountain C section ; Hambast Formation, 1.35 m below the top; illustrated in Fig. 41A ; MB.C.29941 .

Paratypes IRAN • 1 specimen; Esfahan Province, Baghuk Mountain 1 section ; Hambast Formation; MB.C.29938 • 2 specimens; Esfahan Province, Baghuk Mountain B section ; Hambast Formation; MB.C.29939 to MB.C.29940 • 14 specimens; Esfahan Province, Baghuk Mountain E section ; Hambast Formation; MB.C.29942 to MB.C.29955 • 2 specimens; Esfahan Province, Baghuk Mountain F section ; Hambast Formation; MB.C.29956 to MB.C.29957 • 2 specimens; Esfahan Province, Baghuk Mountain G section ; Hambast Formation; MB.C.29958 to MB.C.29959 • 2 specimens; Esfahan Province, Baghuk Mountain H section ; Hambast Formation; MB.C.29960 to MB.C.29961 .

Description

Holotype MB.C.29941 is a rather well-preserved specimen of 64 mm conch diameter and shows all typical characters for the species ( Fig. 41A ). The specimen shows one and a half whorls preserved. It displays septal crowding and the end of the phragmocone appears at 38 mm diameter.About 210 degrees of the last volution belong to the body chamber, which shows a weakly trapezoidal whorl profile with weakly concave, weakly diverging flanks, a subangular ventrolateral shoulder and a flattened tectiform venter. The whorl belonging to the phragmocone has a more pronounced trapezoidal profile with convex, diverging flanks. The sculpture on the phragmocone part consists of rather small, pointed ventrolateral tubercles, 22 per volution. On the body chamber, these tubercles are connected with weak and rounded radial ribs, which are strongest on the inner flank.

Paratype MB.C.29946 is a similar specimen with 58 mm conch diameter and the last septum at 33 mm dm ( Fig. 41B ). It possesses a nearly quadrate whorl cross section of the body chamber but also shows that the profile is trapezoidal in an earlier growth stage. On the last volution of the phragmocone, 20 sharp ventrolateral nodes can be counted.

Larger paratypes such as MB.C.29947 (50 mm phragmocone diameter), MB.C.29944 (52 mm; Fig. 42B ), MB.C.29938 (52 mm; Fig. 42A ) and MB.C.29958 (53 mm; Fig. 43A ) are generally similar but show stronger diverging flanks of the body chamber.

Suture lines were drawn from four specimens, all of them show principally similar outlines with some common characters ( Fig. 43B–E ). The external lobe is not as deep as the adventive lobe, it is wider at its base, from where the flanks converge towards the ventrolateral saddle. All four specimens show asymmetric notching of its prongs; usually there are three notches but also more intense serration is possible. The ventrolateral saddle is usually slightly inflated and the adventive lobe is parallel-sided with five or six notches at its base.

Remarks

Clivotirolites decoratus gen. et sp. nov. differs in the large number (more than 20 per volution) of ventrolateral nodes from the species of Clivotirolites petilus gen. et sp. nov. (about 15 nodes per volution).

Stratigraphic range

Upper part of the Hambast Formation; 2.05 to 1.10 m below the extinction horizon ( Alinashites ferdowsii Zone to Abichites abichi Zone ).

Figures

Fig. 41. Clivotirolites decoratus Korn & Hairapetian gen. et sp. nov., lateral and dorsal views.A. Holotype MB.C.29941, section C, -1.35 m. B. Paratype MB.C.29946, section E, float. Scale bar units =1 mm.

Fig. 42. Clivotirolites decoratus Korn & Hairapetian gen. et sp. nov., lateral and dorsal views.A. Paratype MB.C.29938, section 1, -1.50 m. B. Paratype MB.C.29944, section E, float. Scale bar units =1 mm.

Fig. 43. Clivotirolites decoratus Korn & Hairapetian gen. et sp. nov. A. Lateral view, paratype MB.C.29958, section G, float. B. Suture line, paratype MB.C.29938, at 17.8 mm wh. C. Suture line, paratype MB.C.29944, at 15.6 mm wh.D. Suture line, holotype MB.C.29941, at 13.2 mm wh. E. Suture line, paratype MB.C.29946, at 13.0 mm ww, 11.2 mm wh. F. Whorl profile proportions. Abbreviations: see Material and methods. Scale bar units =1 mm.