Abichites alibashiensis 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 : 89-91

Abichites alibashiensis Korn & Ghaderi in Korn et al., 2016

Fig. 57 ; Table 31

Abichites alibashiensis Korn & Ghaderi in Korn et al., 2016: 879, text-fig. 36.

Diagnosis

Species of Abichites with conch reaching 85 mm dm. Subadult stage with broadly oval, weakly depressed whorl profile (ww/wh =1.10–1.30) and rounded venter; 12–15 ventrolateral nodes per volution. Adult stage with quadrate of weakly subtrapezoidal, weakly compressed whorl profile (ww/wh =0.80–1.25),

flattened venter and subangular to angular ventrolateral shoulder; sharp ribs. Prongs of external lobe simple or bifid; altogether 7–11 notches of E, A and L lobes.

Material examined

Holotype IRAN • East Azerbaijan, Ali Bashi N section ; Paratirolites Limestone , 1.40 m below the top; illustrated by Korn & Ghaderi in Korn et al. (2016: text-fig. 36a); MB.C.25399 .

Additional material

IRAN • 2 specimens; Esfahan Province, Baghuk Mountain 1 section ; Hambast Formation; MB.C.30041 to MB.C.30042 • 3 specimens; Esfahan Province, Baghuk Mountain B section ; Hambast Formation; MB.C.30043 to MB.C.30045 • 3 specimens; Esfahan Province, Baghuk Mountain C section ; Hambast Formation; MB.C.30046 to MB.C.30048 • 5 specimens; Esfahan Province, Baghuk Mountain E section ; Hambast Formation; MB.C.30049 to MB.C.30053 • 1 specimen; Esfahan Province, Baghuk Mountain F section ; Hambast Formation; MB.C.30054 • 4 specimens; Esfahan Province, Baghuk Mountain G section ; Hambast Formation; MB.C.30055 to MB.C.30058 .

Description

Specimen MB.C.30051 has 62 mm conch diameter and is rather well preserved with about 190 degrees of the body chamber visible ( Fig. 57A ). The whorl profile of the terminal body chamber has a broadly rounded umbilical margin, weakly concave flanks that are gently converging towards the flat venter, which is deliminated by an angular ventrolateral shoulder. In the phragmocone, the whorl profile is oval with a broadly rounded venter. The change of the sculpture from the subadult stage with coarse ventrolateral nodes (12 per volution) towards the adult stage with only weak ribs on the flank happens already before the beginning of the terminal body chamber.

Specimen MB.C.30046 is smaller (48 mm dm) and shows the transformation from the subadult stage with rounded ventrolateral margin to the adult stage with quadrate whorl profile, in which the venter is flat and separated from the flanks by an angular margin ( Fig. 57B ). The sculpture of the subadult stage possesses prominent ribs (about 13 per volution), which weaken out on the terminal body chamber. The suture line of specimen MB.C.30046 shows a simply subdivided external lobe with narrow, V-shaped prongs, a broadly rounded parabolic ventrolateral saddle and asymmetric, weakly serrated adventive and lateral lobes ( Fig. 57D ).

Remarks

Abichites alibashiensis differs from A. abichi , A. stoyanowi and A. subtrapezoidalis in the sharp ribs, which tend to end in ventrolateral nodes, in the subadult stage. Species of Alibashites possess subadult ribs but also ventrolateral nodes; these are A. mojsisovicsi (with very weak adult ribs) and A. ferdowsii (with a much more depressed whorl profile).

Stratigraphic range

Upper part of the Hambast Formation; 1.15 to 0.40 m below the extinction horizon ( Abichites abichi Zone to lowest part of the Arasella minuta Zone ).

Figures

Fig. 57.Abichites alibashiensis Korn &Ghaderi, 2016.A. Lateral and dorsalview, specimen MB.C.30051, section E, float. B. Lateral and dorsal view, specimen MB.C.30046, section C, -0.50 m. C. Lateral and dorsal view, specimen MB.C.30045, section B, float. D. Suture line, specimen MB.C.30046, at 10.1 mm wh. E. Whorl profile proportions. Abbreviation: see Material and methods. Scale bar units =1 mm.