Abichites abichi Shevyrev, 1965

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 : 87-89

Abichites abichi Shevyrev, 1965

Fig. 56 ; Table 30

Abichites abichi Shevyrev, 1965: 181 , pl. 24 fig. 4.

Xenodiscus aff. kapila – Stoyanow 1910: 87, pl. 9 fig. 3. Abichites abichi – Shevyrev 1968: 96, pl. 4 fig. 4. — Korn & Ghaderi in Korn et al. 2016: 878, textfig. 35.

Diagnosis

Species of Abichites with conch reaching 75 mm dm. Subadult stage with subquadrate, weakly depressed to compressed whorl profile (ww/wh =1.20) and slightly flattened venter; with 15 rounded straight ribs on the flanks. Adult stage with quadrate whorl profile (ww/wh =1.00), parallel flanks and flattened venter; with weak rounded ribs on the flanks. Prongs of external lobe usually simple; 7–12 notches of E, A and L lobes.

Type material

Holotype AZERBAIJAN • Nakhichevan Province, Dorasham 2 section ; Paratirolites Limestone ; illustrated by Shevyrev (1965: pl. 24 fig. 4); PIN 1252/137 .

Material examined

IRAN • 4 specimens; Esfahan Province, Baghuk Mountain 1 section ; Hambast Formation; MB.C.30019 to MB.C.30022 • 1 specimen; Esfahan Province, Baghuk Mountain B section ; Hambast Formation; MB.C.30023 • 5 specimens; Esfahan Province, Baghuk Mountain C section ; Hambast Formation; MB.C.30024 to MB.C.30028 • 6 specimens; Esfahan Province, Baghuk Mountain C section ; Hambast Formation; MB.C.30029 to MB.C.30034 • 4 specimens; Esfahan Province, Baghuk Mountain G section ; Hambast Formation; MB.C.30035 to MB.C.30038 • 2 specimens; Esfahan Province, Baghuk Mountain H section ; Hambast Formation; MB.C.30039 to MB.C.30040 .

Description

Specimen MB.C.30039 has 44 mm diameter and is a fragment of half a volution ( Fig. 56A ). However, it allows the study of the conch shape with a nearly quadrate whorl profile. On half of a volution there are twelve sharp radial ribs, which are coarsest in the outer flank.

Specimen MB.C.30019 has 40 mm conch diameter and allows the study of only one volution ( Fig. 56B ). The whorl profile is subtrapezoidal with broadly rounded umbilical margin, weakly converging flanks, a subangular ventrolateral shoulder and a flat venter. The sculpture is weaker than in the first specimen and the ribs are coarsest on the inner flank.

The suture line of specimen MB.C.30019 is characterised by a large external lobe, of which the flanks stand parallel in the middle part. Its prongs are narrowly V-shaped and non-serrated. After a ventrolateral saddle that is as wide as the external lobe follow a small, nearly parallel-sided adventive lobe with three notches, a small lateral saddle and a small parallel-sided lateral lobe with three notches ( Fig. 56C ).

Remarks

Abichites abichi differs from the otherwise similar species A. subtrapezoidalis in the quadrate adult whorl profile (subtrapezoidal in A. subtrapezoidalis ). The body chamber of A. abichi has stronger ribs than A. subtrapezoidalis does. A. alibashiensis has a similar body chamber, but differs from A. abichi in the coarse ventrolateral nodes of the subadult stage.

Stratigraphic range

Upper part of the Hambast Formation; 1.20 to 0.05 m below the extinction horizon ( Abichites abichi Zone to Arasella minuta Zone ).

Figures

Fig. 56. Abichites abichi Shevyrev, 1965. A. Lateral and dorsal view, specimen MB.C.30039, section H, -1.30 m. B. Lateral and dorsal view, specimen MB.C.30019, section 1, -0.90 m. C. Suture line, specimen MB.C.30019, at 7.7 mm wh. D. Whorl profile proportions. Abbreviation: see Material and methods. Scale bar units= 1 mm.