Stoyanowites dieneri ( Stoyanow, 1910 )

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 : 97-98

Stoyanowites dieneri ( Stoyanow, 1910)

Fig. 61 , Table 35

Paratirolites Dieneri Stoyanow, 1910: 83 , pl. 8 fig. 2.

Paratirolites dieneri – Spath 1934: 366, text-fig. 125e. — Shevyrev 1965: 178, pl. 23 figs 2–3; 1968: 93, pl. 3 figs 2–3.

Stoyanowites dieneri – Korn in Ghaderi et al. 2014: text-fig. 7F. — Korn & Ghaderi in Korn et al. 2016: 884, text-fig. 42.

Paratirolites mojsisovicsi – Teichert & Kummel in Teichert et al. 1973: pl. 7 fig. 1.

Diagnosis

Species of Stoyanowites with conch reaching 120 mm dm. Subadult stage with oval, weakly compressed whorl profile (ww/wh =0.70–0.80) and rounded venter; 16 fine ribs forming weak and rounded dorsolateral and ventrolateral nodes. Adult stage with parallel flanks and weakly compressed whorl profile (ww/wh =0.60–0.70), rounded venter and subangular ventrolateral shoulder; weak dorsolateral nodes. Prongs of external lobe bifid; altogether 10–16 notches of E, A and L lobes; external lobe shorter than adventive lobe.

Material examined

IRAN • 3 specimens; Esfahan Province, Baghuk Mountain E section ; Hambast Formation; MB.C.30089 to MB.C.30091 • 1 specimen; Esfahan Province, Baghuk Mountain H section ; Hambast Formation; MB.C.30092 • 4 specimens; Esfahan Province, Baghuk Mountain section ; Hambast Formation; MB.C.30093 to MB.C.30096 .

Description

Specimen MB.C.30090 has 74 mm conch diameter and is fairly well preserved if partly crushed and weathered ( Fig. 61A ). Nearly half of the last volution belongs to the body chamber. At the end of the preserved part of the body chamber, the whorl profile is compressed (ww/wh= 0.70) and has nearly parallel, only weakly converging flanks, a subangular ventrolateral shoulder and a flat venter. One volution earlier, the whorl profile is oval with rounded venter. The sculpture on the body chamber consists of faint radial riblets and pronounced isolated ventrolateral spines, ten per half volution. The penultimate volution is corroded, but it appears that the sculpture is weaker than on the terminal body chamber.

The suture line of specimen MB.C.30090 has the characteristic short external lobe with bifid, nearly parallel-sided prongs ( Fig. 61C ). Both the adventive lobe and the lateral lobe are also nearly parallelsided, they show four small notches.

The smaller specimen MB.C.30089 has a weaker sculpture than the preceding specimen ( Fig. 61B ). It shows weak ventrolateral spines and weak radial plications on the flank. Its suture line has a weakly pouched, short external lobe with bifid prongs; the pouched adventive lobe and the parallel-sided lateral lobes are trifid ( Fig. 61D ).

Remarks

Stoyanowites dieneri differs from S. aspinosus , which is clearly separated from S. dieneri because of its wider umbilicus and the lack of spines. Stoyanowites parallelus sp. nov. differs in the flat venter and the more numerous ribs and ventrolateral spines.

Stratigraphic range

Upper part of the Hambast Formation; the only one in situ collected specimen comes from 1.80 m below the extinction horizon ( Alibashites ferdowsii Zone ).

Figures

Fig. 61. Stoyanowites dieneri (Stoyanow, 1910). A. Lateral and dorsal view, specimen MB.C.30090, section E, float. B. Lateral and dorsal view, specimen MB.C.30089, section E, float. C. Suture line, specimen MB.C.30090, at 12.4 mm ww, 17.4 mm wh. D. Suture line, specimen MB.C.30089, at 14.4 mm wh. E. Whorl profile proportions. Abbreviations: see Material and methods. Scale bar units =1 mm.