Lutites lyriformis 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 : 78-81

Lutites lyriformis Korn & Hairapetian gen. et sp. nov.

urn:lsid:zoobank.org:act:3FC3DB4D-AA14-43A6-B982-0137ED22D6B7

Figs 51–52 ; Table 26

Diagnosis

Species of Lutites gen. nov. with conch reaching 140 mm dm. Subadult stage with parallel-sided, compressed whorl profile (ww/wh = 0.60–0.70) and rounded venter; about 14 ventrolateral nodes per volution. Adult stage with subtrapezoidal, compressed whorl profile (ww/wh =0.50–0.60), concave flanks, concave venter and angular ventrolateral shoulder; numerous weak and densely arranged ribs. Prongs of external lobe bifid to multiply serrated; altogether 13–22 notches of E, A and L lobes.

Etymology

From the Latin ‘ lyra ’, referring to the shape of the whorl profile.

Material examined

Holotype IRAN • Esfahan Province, Baghuk Mountain A section ; Hambast Formation; illustrated in Fig. 51A ; MB.C.29995 .

Paratypes IRAN • 1 specimen; Esfahan Province, Baghuk Mountain 1 section ; Hambast Formation; MB.C.29994 • 2 specimens; Esfahan Province, Baghuk Mountain C section ; Hambast Formation; MB.C.29996 to MB.C.29997 • 1 specimen; Esfahan Province, Baghuk Mountain E section ; Hambast Formation; MB.C.29998 • 1 specimen; Esfahan Province, Baghuk Mountain G section ; Hambast Formation; MB.C.29999 • 2 specimens; Esfahan Province, Baghuk Mountain H section ; Hambast Formation; MB.C.30000 to MB.C.30001 .

Description

Holotype MB.C.29995 is a rather well-preserved specimen with 96 mm conch diameter ( Fig. 51A ). It allows the study of three and a half volutions, of which only one third of a volution belongs to the body chamber. Adulthood is indicated by the weak crowding of the last septa at 73 mm diameter. The whorl profile is, at the largest preserved conch diameter, subtrapezoidal with a broadly rounded umbilical margin and concave and converging flanks. The weakly concave venter is separated from the flanks by an angular ventrolateral shoulder. Half a volution earlier, the venter is plane and another half a volution back, the venter is broadly rounded. The sculpture shows significant ontogenetic changes from the subadult stage with 13 coarse and blunt ventrolateral nodes, which originate from weak and rounded radial ribs, per volution. They become weaker and more numerous in the last quarter volution of the phragmocone (about 12 weak ventrolateral nodes within this interval). The body chamber possesses a very weak sculpture consisting only of weak and rounded radial riblets in the inner flank area.

The suture line of the holotype possesses a parallel-sided external lobe with prongs being asymmetrically serrated by four and five small notches, respectively. The asymmetric ventrolateral saddle is nearly as wide as high; it is followed by an adventive lobe with oblique base serrated into seven small notches. The weakly asymmetric, inverted U-shaped lateral saddle is nearly as high as the ventrolateral saddle. Finally, the asymmetric lateral lobe has also seven small notches ( Fig. 52A ).

The smaller paratype MB.C.29997 has 74 mm conch diameter, of which the phragmocone has a diameter of 64 mm and one quarter of a whorl belongs to the body chamber ( Fig. 51B ). The whorl profile is subtrapezoidal with concave, converging flanks and the venter is weakly concave. The sculpture generally resembles the holotype, but the ribs and nodes are weaker. The same is true for the additional

paratypes MB.C.29996 ( Fig. 51C ) and MB.C.29999 ( Fig. 51D ), which is the conch geometry are nearly identical with the holotype.

The suture line of paratype MB.C.29997 shows a parallel-sided external lobe that is deeper than the adventive lobe. The prongs are bifid and parallel-sided. All lobes and thus saddles are parallel-sided and all saddles have the same height. The adventive lobe and the lateral lobe possess six and four small notches ( Fig. 52B ).

Remarks

The new species differs in the coarse ventrolateral nodes of the subadult stage from most of the other species of Lutites gen. nov. with compressed whorl profile. Lutites lyriformis gen. et sp. nov. is similar to L. profundus gen. et sp. nov. but differs in the much weaker sculpture of the terminal body chamber, which shows only very weak ribs in L. lyriformis gen. et sp. nov. but ventrolateral nodes in L. profundus gen. et sp. nov.

Stratigraphic range

Upper part of the Hambast Formation; 1.45 to 1.00 m below the extinction horizon ( Lutites profundus Zone to Abichites abichi Zone ).

Figures

Fig. 51. Lutites lyriformis Korn & Hairapetian sp. nov., lateral and dorsal views. A. Holotype MB.C.29995, section A, float. B. Paratype MB.C.29997, section C, -1.00 m. C. Paratype MB.C.29996, section C, -1.45 m. D. Paratype MB.C.29999, section G, -1.20 m. Scale bar units =1 mm.

Fig. 52. Lutites lyriformis Korn & Hairapetian gen. et sp. nov. A. Suture line, holotype MB.C.29995, at 58.3 mm dm, 23.1 mm wh. B. Suture line, paratype MB.C.29997, at 53.8 mm dm, 19.0 mm wh. C. Whorl profile proportions. Abbreviations: see Material and methods. Scale bar units =1 mm.