Paratirolites baghukensis 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 : 49-52

Paratirolites baghukensis Korn & Hairapetian sp. nov.

urn:lsid:zoobank.org:act:27027DEB-9F15-4F61-8EA3-3F15E997A1D9

Figs 33–34 ; Table 16

Diagnosis

Species of Paratirolites with conch reaching 130 mm dm. Subadult stage with trapezoidal, weakly depressed whorl profile (ww/wh =1.00–1.20) and rounded venter; about 12 moderately coarse ribs ending in conical ventrolateral nodes per volution. Adult stage with trapezoidal and weakly compressed whorl profile (ww/wh =0.70–0.90), flattened tectiform venter and subangular ventrolateral shoulder; numerous sharp ribs ending in sharp radially elongated ventrolateral nodes. Prongs of external lobe usually trifid; altogether 13–15 notches of E, A and L lobes.

Etymology

Named after the occurrence at Baghuk Mountain.

Material examined

Holotype IRAN • Esfahan Province, Baghuk Mountain G section ; Hambast Formation; illustrated in Fig. 33A ; MB.C.29868 .

Paratypes IRAN • 2 specimens; Esfahan Province, Baghuk Mountain 1 section ; Hambast Formation; MB.C.29849 to MB.C.29850 • 4 specimens; Esfahan Province, Baghuk Mountain A section ; Hambast Formation; MB.C.29851 to MB.C.29854 • 5 specimens; Esfahan Province, Baghuk Mountain C section ; Hambast Formation; MB.C.29855 to MB.C.29859 • 8 specimens; Esfahan Province, Baghuk Mountain E section ; Hambast Formation; MB.C.29860 to MB.C.29867 • 7 specimens; Esfahan Province, Baghuk Mountain G section ; Hambast Formation; MB.C.29869 to MB.C.29875 • 1 specimen; Esfahan Province, Baghuk Mountain H section ; Hambast Formation; MB.C.29876 • 3 specimens; Esfahan Province, Baghuk Mountain ; Hambast Formation; MB.C.29877 to MB.C.29879 .

Description

Holotype MB.C.29868 has 70 mm conch diameter and is fairly well-preserved but slightly corroded. The last third of the terminal volution belongs to the body chamber (which is thus only incompletely preserved); adulthood of the specimen is obvious because of the crowding of the last septa of the phragmocone ( Fig. 33A ). The penultimate of the preserved whorls shows a trapezoidal profile with a rounded venter. The body chamber finally shows a trapezoidal whorl profile with weakly diverging flanks, an angular ventrolateral shoulder and a nearly flat, tectiform venter. The sculpture changes with the beginning of the terminal body chamber, but this change is continuous without sudden breaks. One subadult volution has ten isolated spiny ventrolateral nodes.Already towards the end of the phragmocone, these nodes become radially elongate and form coarse ribs across the flank. At the beginning of the terminal body chamber, the ventrolateral nodes weaken and finally, only sharp ribs, about 15 per quarter of a volution, are present.

The suture line of holotype MB.C.29868 shows a slightly pouched external lobe with trifid, asymmetric prongs. The ventrolateral saddle is weakly inflated, the adventive and lateral lobes are flattened at the base and subdivided in five and four notches, respectively ( Fig. 33C ).

Paratype MB.C.29860 ( Fig. 33B ) is smaller with 61 mm conch diameter but confirms the description given for the holotype. It shows four whorls preserved and thus allows for the study of the sculpture of the inner volutions.

The two larger paratypes MB.C.29874 and MB.C.29850 ( Fig. 34 ) show then the transformation into the weakly ornamented adult stage, in which a tendency towards a parallel-sided whorl profile is visible.

Remarks

Paratirolites baghukensis sp. nov. belongs to the slender species of the genus. It differs from the other species of the genus in the sharp ribs on the adult body chamber. Paratirolites multiconus also has a slender conch, but differs from P. baghukensis sp. nov. in the much more numerous ventrolateral nodes.

Stratigraphic range

Upper part of the Hambast Formation; 3.10 to 2.35 m below the extinction horizon ( Paratirolites kittli Zone ).

Figures

Fig. 33. Paratirolites baghukensis Korn & Hairapetian sp. nov. A–B. Lateral and dorsal views. A. Holotype MB.C.29868, section G, float. B. Paratype MB.C.29860, section E, -2.55 m. C. Suture line of holotype MB.C.29868, at 49.0 mm dm, 21.0 mm ww, 16.0 mm wh. D. Whorl profile proportions. Abbreviations: see Material and methods. Scale bar units=1 mm.

Fig. 34. Paratirolites baghukensis Korn & Hairapetian sp. nov. A. Paratype MB.C.29850, section 1, -2.70 m. B. Paratype MB.C.29874, section G, float. Scale bar units= 1 mm.