Abichites infirmis 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 : 96-97

Abichites infirmis Korn & Hairapetian sp. nov.

urn:lsid:zoobank.org:act:DF627B6D-3446-4B02-89B2-81ED420C876D

Fig. 60 ; Table 34

Diagnosis

Species of Abichites with conch reaching 50 mm dm. Subadult stage with oval, weakly compressed whorl profile (ww/wh =0.60–0.80) and rounded venter; very weak, rounded nodes. Adult stage with weakly subtrapezoidal, weakly compressed whorl profile (ww/wh =0.60–0.80) with weakly converging flat flanks, weakly flattened venter and narrowly subangular ventrolateral shoulder. Sculpture with faint plications. Prongs of external lobe simple; altogether 5–6 notches of E, A and L lobes.

Etymology

From the Latin ‘ infirmis ’, meaning ‘barely visible’, because of the weak sculpture.

Material examined

Holotype IRAN • Esfahan Province, Baghuk Mountain G section ; Hambast Formation, 0.40 m below the top; illustrated in Fig. 60A ; MB.C.30086 .

Paratypes IRAN • 1 specimen; Esfahan Province, Baghuk Mountain 1 section ; Hambast Formation; MB.C.30083 • 1 specimen; Esfahan Province, Baghuk Mountain C section ; Hambast Formation; MB.C.30084 • 1 specimen; Esfahan Province, Baghuk Mountain E section ; Hambast Formation; MB.C.30085 • 2 specimens; Esfahan Province, Baghuk Mountain G section ; Hambast Formation; MB.C.30087 to MB.C.30088 .

Description

Holotype MB.C.30086 is a rather well-preserved specimen with 42 mm conch diameter ( Fig. 60A ). The whorl profile of the body chamber is subtrapezoidal with a narrowly rounded umbilical margin, flat and weakly converging flanks, a subangular ventrolateral shoulder and a flattened but still broadly rounded venter. Its ww/wh ratio is 0.70 and the whorl embraces the preceding one only weakly. The shell appears to be smooth except for very faint plications.

The suture line of the holotype has a parallel-sided external lobe that has a width/depth ratio of ~ 0.75. It is deeper than the adventive lobe and possesses unsubdivided lanceolate prongs. The ventrolateral saddle is inverted U-shaped and symmetric and the weakly asymmetric, parallel-sided adventive lobe is subdivided into two secondary notches. The narrow lateral saddle is also inverted U-shaped and followed by a parallel-sided lateral lobe with two notches ( Fig. 60B ).

Remarks

Abichites infirmis differs from most of the species of the genus in the lack of coarse ribs or nodes. Similar species are A. paucinodus (which possesses few coarse nodes on the flanks) and A. terminalis (with an oval whorl profile).

Stratigraphic range

Upper part of the Hambast Formation; 0.40 to 0.05 m below the extinction horizon ( Arasella minuta Zone ).

Figures

Fig. 60. Abichites infirmis Korn & Hairapetian sp. nov.A. Lateral and dorsal view, holotype MB.C.30086, section G, -0.40 m. B. Suture line, holotype MB.C.30086, at 21.5 mm dm, 9.1 mm wh. Abbreviations: see Material and methods. Scale bar units=1 mm.