Paratirolites vediensis Shevyrev, 1965

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 : 40-43

Paratirolites vediensis Shevyrev, 1965

Figs 28–29 ; Table 12

Paratirolites vediensis Shevyrev, 1965: 176 , pl. 23 fig. 1.

Paratirolites vediensis – Shevyrev 1968: 92, pl. 5 fig. 1. — Stepanov et al. 1969: pl. 13 fig. 5. — Korn in Ghaderi et al. 2014: text-fig. 7g. — Korn & Ghaderi in Korn et al. 2016: 864, text-figs 23–24.

Diagnosis

Species of Paratirolites with conch reaching 250 mm dm. Subadult stage with trapezoidal, weakly depressed whorl profile (ww/wh = 1.20–1.50) and flattened tectiform venter; 10–15 coarse ventrolateral nodes per volution. Adult stage with strongly trapezoidal and weakly depressed whorl profile (ww/ wh= 1.00–1.20), flattened tectiform venter and angular ventrolateral shoulder; weak ventrolateral nodes. Prongs of external lobe usually multiply serrated; altogether 12–20 notches of E, A and L lobes.

Type material

Holotype ARMENIA • 1 specimen; Vedi ; Paratirolites Limestone ; illustrated by Shevyrev (1965: pl. 23 fig.1); PIN 1478/2 .

Material examined

IRAN • 6 specimens; Esfahan Province, Baghuk Mountain 1 section ; Hambast Formation; MB.C.29785 to MB.C.29790 • 1 specimen; Esfahan Province, Baghuk Mountain A section ; Hambast Formation; MB.C.29791 • 4 specimens; Esfahan Province, Baghuk Mountain C section ; Hambast Formation; MB.C.29792 to MB.C.29795 • 4 specimens; Esfahan Province, Baghuk Mountain E section ; Hambast Formation; MB.C.29796 to MB.C.29799 • 6 specimens; Esfahan Province, Baghuk Mountain G section ; Hambast Formation; MB.C.29800 to MB.C.29805 • 5 specimens; Esfahan Province, Baghuk Mountain H section ; Hambast Formation; MB.C.29806 to MB.C.29810 • 2 specimens; Esfahan Province, Baghuk Mountain section ; Hambast Formation; MB.C.29811 to MB.C.29812 .

Description

Specimens MB.C.29811 and MB.C.29794 are the largest specimens with terminal phragmocone diameters of approximately 85 mm. They indicate that the maximum diameter including body chamber has been about 155 mm. Unfortunately, both specimens are poorly preserved.

Specimen MB.C.29804 (100 mm dm; Fig. 28A ) shows septal crowding at a phragmocone diameter of 65 mm, which means that the maximum conch diameter was approximately 120 mm. It is slightly corroded but shows that the shape of the whorl profile is trapezoidal in the subadult and adult stage. The venter becomes flat with an angular ventrolateral shoulder during formation of the terminal body chamber but is more flattened in the phragmocone stage. The specimen shows a sculpture of the phragmocone that consists of 12 coarse conical nodes on the ventrolateral shoulder and both specimens demonstrate that these nodes become continuously weaker and more numerous (15 on half a volution in) on the body chamber. Specimen MB.C.29798 (88 mm dm; Fig. 28B ) closely resembles specimen MB.C.29804 but possesses more longitudinally elongate ventrolateral spines.

The two smaller specimens MB.C.29792 ( Fig. 29A ) and MB.C.29785 ( Fig. 29B ), both with about 50 mm conch diameter, are rather well preserved phragmocones. Both possess trapezoidal whorl profiles (ww/ wh= 1.65–1.75) with strongly diverging flattened flanks, a subangular or angular ventrolateral shoulder and a slightly flattened, tectiform venter. The sculpture consists of 11 or 12 spiny ventrolateral nodes per volution, which begin as isolated nodes and develop to spiny nodes that show a rib-alike elongation toward the umbilicus.

The suture lines of the two specimens resemble each other ( Fig. 29C–D ) and possess a parallel-sided external lobe that is as deep as the adventive lobe. Its prongs are narrow and parallel-sided with three small notches. The ventrolateral saddle is inflated and asymmetric and the lateral saddle reaches only half the height of the ventrolateral saddle. The adventive lobe is asymmetric in both specimens and dorsally inclined; it is serrated with 6 and 8 little notches, respectively.

Remarks

The material from Baghuk Mountain closely resembles, in conch shape and ornament, the material from the type area near Julfa, but differs in the maximum conch size. While the maximum phragmocone diameter of the Julfa material ranges between 70 and 128 dm (Korn & Ghederi in Korn et al. 2016), the Baghuk Mountain material reaches 85 mm only.

Paratirolites vediensis differs from P. kittli in the strongly trapezoidal whorl profile with a flattened venter of the subadult stage, which shows a rounded venter in P. kittli . It differs from P. trapezoidalis , which possesses a very similar conch geometry, in the much coarser ribs of the adult stage (which in P. trapezoidalis are much more numerous and delicate), and in the stronger serrated prongs of the external lobes (usually multiply serrated in P. vediensis , but simple or bifid in P. trapezoidalis ).

Stratigraphic range

Upper part of the Hambast Formation; 3.10 to 2.40 m below the extinction horizon ( Paratirolites kittli Zone ).

Figures

Fig. 28. Paratirolites vediensis Shevyrev, 1965, lateral and dorsal views. A. Specimen MB.C.29804, section G, -2.75 m. B. Specimen MB.C.29798, section E, float. Scale bar units= 1 mm.

Fig. 29. Paratirolites vediensis Shevyrev, 1965. A–B. Lateral and dorsal views. A. Specimen MB.C.29792, section C, -2.75 m. B. Specimen MB.C.29785, section 1, -2.80 m. – C–D. Suture lines. C. Specimen MB.C.29792, at 13.0 mm wh. D. Specimen MB.C.29785, at 12.8 mm wh. – E. Whorl profile proportions. Abbreviations: see Material and methods. Scale bar units= 1 mm.