Esfahanites armatus 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 : 68-71

Esfahanites armatus Korn & Hairapetian gen. et sp. nov.

urn:lsid:zoobank.org:act:DACEC5B2-4BE5-40D0-AA2B-578741DC349C

Figs 45–46 ; Table 22

? Paratirolites sp. Ghaedi et al., 2009: pl. 2 figs 1, 4.

? Paratirolites waageni – Zakharov & Mussavi Abnavi 2013: text-fig. 12c.

Diagnosis

Species of Esfahanites gen. nov. with conch reaching 130 mm dm. Subadult stage with strongly trapezoidal, moderately depressed whorl profile (ww/wh =1.50–1.70) and rounded to tectiform venter; about 12 coarse ventrolateral nodes per volution. Adult stage with trapezoidal and moderately depressed whorl profile (ww/wh =1.50–1.70), flattened tectiform venter and angular ventrolateral shoulder; coarse rursiradiate ribs. Prongs of external lobe trifid or multiply serrated; altogether 15–21 notches of E, A and L lobes.

Etymology

From the Latin ‘ armatus ’, meaning ‘armed’, because of the coarse spiny sculpture.

Material examined

Holotype IRAN • Esfahan Province, Baghuk Mountain E section ; Hambast Formation; illustrated in Fig. 45 ; MB.C.29964 .

Paratypes IRAN • 1 specimen; Esfahan Province, Baghuk Mountain A section ; Hambast Formation; MB.C.29963 • 1 specimen; Esfahan Province, Baghuk Mountain E section ; Hambast Formation; MB.C.29965 • 1 specimen; Esfahan Province, Baghuk Mountain G section ; Hambast Formation; MB.C.29966 • 2 specimens; Esfahan Province, Baghuk Mountain H section ; Hambast Formation; MB.C.29967 to MB.C.29968 .

Description

Holotype MB.C.29964 is the best-preserved specimen; it has 106 mm conch diameter and allows the study of two whorls ( Fig. 45A ). The diameter of the phragmocone is 68 mm and the body chamber has a length of about 270 degrees. Throughout the last two preserved volutions, the whorl profile is trapezoidal, but with the flanks less strongly diverging at the end of growth. The venter is broadly rounded in the penultimate whorl and becomes more flattened on the terminal body chamber. The sculpture on the phragmocone has 14 coarse conical ventrolateral nodes on the last volution; these nodes show a rib-like elongation towards the umbilicus. The sculpture on the body chamber shows variably coarse, rounded ribs on the flank; they turn backward near the umbilicus and are strengthened in the ventrolateral area.

The suture line of holotype MB.C.29964 is remarkable because of its very small external lobe, which is wider at the base and is constricted in the upper part ( Fig. 45B ). The prongs are inclined ventrally and possess five little notches each. The ventrolateral saddle is small and inflated. The asymmetric adventive lobe is strongly serrated with little notches being developed on the ventral side up to half of the lobe depth. The lateral lobe is slightly less strongly serrated than the adventive lobe.

Paratype MB.C.29966 is an incomplete but otherwise rather well-preserved individual of 101 mm conch diameter; it allows the study of two and a half whorls ( Fig. 46A ). The body chamber begins at 60 mm conch diameter, meaning that the preserved part of the body chamber has a length of 270 degrees and is nearly complete. Conch shape changes can be observed during the last whorl of the specimen. While the whorl profile is circular with rounded venter at the binning of the last whorl, it changes to tectiform and has, at the end of growth, an almost flat venter, separated from the flat and diverging flanks by an angular ventrolateral shoulder. The sculpture of the phragmocone part of the specimen shows coarse conical nodes in the ventrolateral area, 12 on the last volution and 10 on the penultimate volution. At the beginning of the terminal body chamber, these nodes are transformed into elongate nodes and finally rounded ribs, which turn from the umbilicus in backward direction. Finally, at the end of the body chamber these ribs become weaker and only shallow rounded ribs and weak ventrolateral nodes can be seen.

The suture line of paratype MB.C.29966 shows a very small external lobe that has not half the depth of the adventive lobe ( Fig. 46B ). It is parallel-sided with parallel-sided prongs that possess three small

notches. The ventrolateral saddle is inverted U-shaped with a much longer dorsal flank. The adventive lobe has seven small notches and the lateral lobe five, both lobes are asymmetric and separated by a low semi-circular lateral saddle.

Remarks

Esfahanites armatus gen. et sp. nov. differs in the very small external lobe from all the species of Paratirolites . It can therefore not be confused with any other species.

Stratigraphic range

Upper part of the Hambast Formation; the only in situ collected specimen comes from 2.00 m below the extinction horizon ( Alibashites ferdowsii Zone ).

Figures

Fig. 45. Esfahanites armatus Korn & Hairapetian gen. et sp. nov., holotype MB.C.29964, section E, float. A. Lateral and dorsal view. B. Suture line, at 58.0 mm dm, 35.0 mm ww, 22.0 mm wh. Abbreviations: see Material and methods. Scale bar units=1 mm.

Fig. 46. Esfahanites armatus Korn & Hairapetian gen. et sp. nov., paratype MB.C.29966, section G, float. A. Lateral and dorsal view. B. Suture line, at 56.0 mm dm, 36.0 mm ww, 19.0 mm wh. Abbreviations: see Material and methods. Scale bar units=1 mm.