Paratirolites coronatus 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 : 46-47

Paratirolites coronatus Korn & Ghaderi in Korn et al., 2016

Fig. 31 ; Table 14

Paratirolites coronatus Korn & Ghaderi in Korn et al., 2016: 860, text-figs 17–18.

Diagnosis

Species of Paratirolites with conch reaching 125 mm dm. Subadult stage with trapezoidal, moderately depressed whorl profile (ww/wh =1.60–1.90) and flattened tectiform venter; 15 coarse conical ventrolateral nodes per volution. Adult stage with extremely trapezoidal and moderately depressed whorl profile (ww/wh =1.60–1.90), flattened tectiform venter and subangular ventrolateral shoulder; weak ventrolateral nodes. Prongs of external lobe trifid or multiply serrated; altogether 11–24 notches of E, A and L lobes.

Material examined

Holotype IRAN • West Azerbaijan, Aras Valley section ; Paratirolites Limestone , 2.90 m below the top; illustrated by Korn et al. (2016: text-fig. 17A); MB.C.25095 .

Additional material

IRAN • 1 specimen; Esfahan Province, Baghuk Mountain E section ; Hambast Formation; MB.C.29842 .

Description

Specimen MB.C.29842 is a fully chambered specimen with 55 mm conch diameter and allows the study of one and a half whorls ( Fig. 31A ). It has a strongly trapezoidal, depressed whorl profile (ww/wh =1.75), weakly sinuous flanks, an angular ventrolateral shoulder and a flattened tectiform venter. Half a volution earlier, the venter is weakly flattened but still rounded and another half volution back, the venter is broadly rounded. The sculpture changes during the last volution of the phragmocone; strong conical nodes at the beginning of this volution are transformed into smaller, longitudinally elongated nodes, which have a position at the ventrolateral shoulder.

The suture line of specimen MB.C.29842 has a V-shaped external lobe with concave flanks and symmetric, narrowly V-shaped simple prongs. The ventrolateral saddle is asymmetric and dorsally inclined and the asymmetric, nearly parallel-sided adventive lobe has nine little notches. The lateral lobe is nearly flat at its base and subdivided in small equally sized notches ( Fig. 31B ).

Remarks

Paratirolites coronatus is the paratirolitid with the widest conch, resulting from the coronate ventrolateral shoulder. Therefore, it cannot be confused with any other species. Paratirolites coronatus differs from P. vediensis and the other species in the more strongly trapezoidal whorl profile of the adult stage.

Stratigraphic range

Upper part of the Hambast Formation; precise horizon at Baghuk Mountain not known.

Figures

Fig. 31. Paratirolites coronatus Korn & Ghaderi, 2015. A. Lateral and dorsal view, specimen MB.C.29842, section E, float. B. Suture line, specimen MB.C.29842, at 48.7 mm dm, 17.8 mm wh. Abbreviations: see Material and methods. Scale bar units=1 mm.