Shevyrevites corrugatus 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 : 22-23

Shevyrevites corrugatus Korn & Hairapetian sp. nov.

urn:lsid:zoobank.org:act:89B3129F-6478-4C46-9CD6-DDCD7C735BF0

Fig. 19 ; Table 4

Diagnosis

Species of Shevyrevites with conch reaching 60 mm dm. Subadult stage with oval, slightly compressed whorl profile (ww/wh = 0.60–0.75) and rounded venter; multiple fine ribs. Adult stage with parallelsided, slightly compressed whorl profile (ww/wh =0.60–0.75), rounded venter and rounded ventrolateral shoulder; multiple fine riblets on the flank. Prongs of external lobe bifid; altogether 11 notches of E, A and L lobes.

Etymology

From the Latin ‘ corrugatus ’, meaning ‘folded’, because of the corrugate sculpture.

Material examined

Holotype IRAN • Esfahan Province, Baghuk Mountain A section ; Hambast Formation; illustrated in Fig. 19B ; MB.C.29718 .

Paratype IRAN • 1 specimen; Esfahan Province, Baghuk Mountain A section ; Hambast Formation; MB.C.29719 ; illustrated in Fig. 19A .

Description

Holotype MB.C.29718 has 37 mm conch diameter and shows half of a volution preserved that belongs to the terminal body chamber ( Fig. 19B ); the maximum phragmocone diameter is 27 mm. The phragmocone

shows rather densely spaced septa (18 per volution), but the last four are then strikingly crowded and indicate adulthood. The conch is extremely discoidal (ww/dm=0.20) and subevolute (uw/dm =0.43) with applanate flanks and a rounded venter. The sculpture consists of numerous densely spaced and sharp radial riblets (about 30 on half a volution in the adult stage), which on the body chamber extend with a shallow concave sinus across the flanks.

The suture line of the holotype has a nearly parallel-sided, weakly pouched external lobe that is almost as deep as the adventive lobe; it has asymmetric prongs that are subdivided by two notches. The slightly asymmetric ventrolateral saddle is inverted U-shaped and followed by the asymmetric adventive lobe with five small notches, an asymmetric lateral saddle and an asymmetric lateral lobe with four notches ( Fig. 19C ).

Remarks

The new species differs from the other species of Shevyrevites by the much weaker sculpture, which consists of feeble riblets in contrast to the coarser ribs in S. shevyrevi and the conical nodes in S. nodosus .

Stratigraphic range

Upper part of the Hambast Formation; float but probably 4.80 m below the extinction horizon (red nodular limestone in the Shevyrevites shevyrevi Zone ).

Figures

Fig. 19. Shevyrevites corrugatus Korn & Hairapetian sp. nov. A. Lateral and dorsal view, paratype MB.C.29719, section A, float. B. Lateral and dorsal view, holotype MB.C.29718, section A, float. C. Suture line, holotype MB.C.29718, at 9.4 mm wh. Abbreviation: see Material and methods. Scale bar units =1 mm.