Stoyanowites parallelus Korn & Hairapetian, 2021

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 : 101-102

Stoyanowites parallelus Korn & Hairapetian sp. nov.

urn:lsid:zoobank.org:act:E6C0C2D8-02EF-4E72-9E1E-78816A50573E

Fig. 63 ; Table 37

Diagnosis

Species of Stoyanowites with conch reaching 100 mm dm. Subadult stage with rectangular, compressed whorl profile (ww/wh =0.70), subangular ventrolateral shoulder and flattened venter; 10 rather coarse ventrolateral spines per half volution. Adult stage with parallel-sided, compressed whorl profile (ww/ wh= 0.60), flat venter and angular ventrolateral shoulder; 15 ventrolateral spines per half volution. Prongs of external lobe simple; altogether 13 notches of E, A and L lobes.

Etymology

Named after the parallel flanks of the whorl profile.

Material examined

Holotype IRAN • Esfahan Province, Baghuk Mountain C section ; Hambast Formation, 1.70 m below the top; illustrated in Fig. 63A ; MB.C.30102 .

Paratypes IRAN • 2 specimens; Esfahan Province, Baghuk Mountain E section ; Hambast Formation; MB.C.30103 to MB.C.30104 • 1 specimen; Esfahan Province, Baghuk Mountain G section ; Hambast Formation; MB.C.30105 .

Description

Holotype MB.C.30102 is an incomplete specimen of 72 mm diameter; it allows the study of conch shape, ornament and suture line. The conch is extremely discoidal (ww/dm= 0.19) with a wide umbilicus (uw/

dm =0.47) and a compressed whorl profile (ww/wh =0.61). It has nearly parallel, slightly concave flanks, a prominent subangular ventrolateral shoulder and a weakly concave venter at the largest diameter ( Fig. 63A ). The sculpture is dominated by coarse ventrolateral spines, which become weaker towards the end of growth, but of which are still 15 are present on half a volution of the body chamber. They are not always connected with short ribs on the inner flank.

The suture line of holotype MB.C.30102 shows the short external lobe, which has simple, weakly pouched prongs. The ventrolateral saddle is rather narrow; the adventive and lateral lobes possess six notches ( Fig. 63B ).

Remarks

Stoyanowites parallelus sp. nov. differs from S. dieneri and S. aspinosus in the flat venter and the numerous sharp ventrolateral nodes in the adult stage.

Stratigraphic range

Upper part of the Hambast Formation; 1.70 m below the extinction horizon ( Alibashites ferdowsii Zone ).

Figures

Fig. 63. Stoyanowites parallelus Korn & Hairapetian sp. nov. A. Lateral and dorsal view, holotype MB.C.30102, section C, -1.70 m. B. Suture line, holotype MB.C.30102, at 17.5 mm wh. Abbreviation: see Material and methods. Scale bar units =1 mm.

Tables

Table 37. Conch dimensions (partly estimated) and ratios of the holotype of Stoyanowites parallelus Korn & Hairapetian sp. nov. from Baghuk Mountain.

Specimen	dm	ww	wh	uw	ah	ww/dm	ww/wh	uw/dm	WER	IZR
MB.C.30102	72.2	13.7	22.5	33.7	21.8	0.19	0.61	0.47	2.05	0.03