Stoyanowites aspinosus 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 : 100-101

Stoyanowites aspinosus Korn & Ghaderi in Korn et al., 2016

Fig. 62 ; Table 36

Stoyanowites aspinosus Korn & Ghaderi in Korn et al., 2016: 885, text-fig. 43.

Diagnosis

Species of Stoyanowites with conch reaching 100 mm dm. Subadult stage with oval, weakly compressed whorl profile (ww/wh =0.70) and rounded venter; 15 narrow and rounded ribs on the flanks. Adult stage with oval and weakly compressed whorl profile (ww/wh = 0.60–0.70) and moderately wide to wide umbilicus (uw/dm =0.40–0.50), rounded venter and rounded ventrolateral shoulder; very weak ribs on the flanks, coarsest in ventrolateral area. Prongs of external lobe bifid; 8–9 notches of E, A and L lobes.

Material examined

Holotype IRAN • West Azerbaijan, Aras Valley section ; Paratirolites Limestone , 0.95 m below the top; illustrated by Korn & Ghaderi in Korn et al. (2016: text-fig. 43a); MB.C.25458 .

Additional material

IRAN • 1 specimen; Esfahan Province, Baghuk Mountain 1 section ; Hambast Formation; MB.C.300978 • 2 specimens; Esfahan Province, Baghuk Mountain A section ; Hambast Formation; MB.C.30098 to MB.C.30099 • 1 specimen; Esfahan Province, Baghuk Mountain C section ; Hambast Formation; MB.C.30100 • 1 specimen; Esfahan Province, Baghuk Mountain E section ; Hambast Formation; MB.C.30101 .

Description

Specimen MB.C.30100 is a fragmentary specimen with 72 mm diameter and shows the wide umbilicus (uw/dm =0.50), the nearly parallel-sided whorl profile and the rounded venter. The ornament of the last half volution consists of numerous (about 25) rather sharp ribles, which extend with a shallow sinus across the flanks and turn forward in the ventrolateral area, where they become coarser and for a hooklike rib ( Fig. 62A ). The venter is smooth.

Remarks

Stoyanowites aspinosus differs from S. dieneri in the absence of dorsolateral nodes and the presence of densely spaced curved riblets on the body chamber. Stoyanowites parallelus sp. nov. differs in the flat venter.

Stratigraphic range

Upper part of the Hambast Formation; 1.80 to 1.60 m below the extinction horizon ( Alibashites ferdowsii Zone ).

Figures

Fig. 62. Stoyanowites aspinosus Korn & Ghaderi, 2016. A. Lateral and dorsal view, specimen MB.C.30100, section C, -1.60 m. B. Whorl profile proportions. Scale bar units =1 mm.