Alibashites mojsisovicsi ( 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 : 71-72

Alibashites mojsisovicsi ( Stoyanow, 1910)

Fig. 47 ; Table 23

Xenodiscus (Paratirolites ?) Mojsisovicsi Stoyanow, 1910: 79, pl. 8 fig. 1.

Abichites mojsisovicsi – Shevyrev 1965: 180, pl. 23 fig. 4; 1968: 95, pl. 4 fig. 3. — Stepanov et al. 1969: pl. 13 fig. 4.

Alibashites mojsisovicsi – Korn & Ghaderi in Korn et al. 2016: 870, text-fig. 29.

Diagnosis

Alibashites with conch reaching 90 mm dm. Subadult stage with circular, weakly depressed whorl profile (ww/wh =1.00–1.20) and rounded venter; 13 coarse ventrolateral nodes per volution. Adult stage with quadrate and weakly compressed whorl profile (ww/wh=0.95–1.00), almost flat venter and subangular

ventrolateral shoulder; low ribs on flanks, forming very weak dorsolateral and ventrolateral nodes. Prongs of external lobe variable, simple to trifid; 8–13 notches of E, A and L lobes.

Material examined

IRAN • 1 specimen; Esfahan Province, Baghuk Mountain C section ; Hambast Formation; MB.C.29969 • 1 specimen; Esfahan Province, Baghuk Mountain H section ; Hambast Formation; MB.C.299670 • 2 specimens; Esfahan Province, Baghuk Mountain ; Hambast Formation; MB.C.299671 to MB.C.29972 .

Description

Specimen MB.C.29969 has 55 mm conch diameter with a moderately well-preserved last volution of the phragmocone but a weathered body chamber ( Fig. 47A ). It possesses a nearly quadrate whorl profile with angular ventrolateral shoulder and weakly concave venter at its largest diameter. Half of a whorl earlier, the venter is nearly flat and another half of a whorl earlier, it is broadly convex. At this stage, the whorl profile is trapezoidal with strongly diverging flanks. The sculpture of the phragmocone shows about 20 ventrolateral nodes with a tendency to become weaker during growth of the conch.

The suture line of specimen MB.C.29969 shows a V-shaped external lobe with diverging flanks, a parallel-sided ventrolateral saddle with weak dorsal inclination and adventive and lateral lobes with moderate serration ( Fig. 47B ). They are separated by a rather low, symmetric lateral saddle.

Remarks

Alibashites ferdowsii also has coarse nodes in the subadult stage like A. mojsisovicsi , but this species shows a much wider whorl profile (ww/wh=1.25–1.50) than A. mojsisovicsi (ww/wh = 0.95–1.00) in the adult stage. A. mojsisovicsi differs from the species of Abichites , which may develop a similar adult stage, in the coarse subadult ventrolateral nodes.

Stratigraphic range

Upper part of the Hambast Formation; 1.35 to 0.75 m below the extinction horizon (upper part of the Lutites profundus Zone to Abichites stoyanowi Zone ).

Figures

Fig. 47. Alibashites mojsisovicsi (Stoyanow, 1910) A. Lateral and dorsal view, specimen MB.C.29969, section C, -0.75 m. B. Suture line, specimen MB.C.29969, at 12.6 mm wh. Abbreviation: see Material and methods. Scale bar units=1 mm.