Paratirolites quadratus Korn & Ghaderi, 2016

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 : 57-59

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 ).

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.

Stratigraphic range

At Baghuk Mountain only known from float from the upper part of the Hambast Formation; Stoyanowites dieneri Zone in the Julfa region.

Figures

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.

Fig. 39. Paratirolites quadratus Korn & Ghaderi, 2016. A. Lateral and dorsal view, specimen MB.C.29933, section E, float. B. Suture line, specimen MB.C.29933, at 29.0 mm ww, 17.0 mm wh. Abbreviations: see Material and methods. Scale bar units=1 mm.