Lutites alius 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 : 83-85

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

urn:lsid:zoobank.org:act:393BE629-C3CF-4FED-A221-1FFD673C8636

Fig. 54 , Table 28

Diagnosis

Species of Lutites gen. nov. with conch reaching 130 mm dm. Subadult stage with oval, compressed whorl profile (ww/wh=0.60–0.70) and rounded venter; very weak, rounded ribs. Adult stage with subtrapezoidal, compressed whorl profile (ww/wh =0.50–0.60), flat or concave venter and angular ventrolateral shoulder; very weak ribs. Prongs of external lobe simple; altogether about 17 notches of E, A and L lobes.

Etymology

From the Latin ‘ alius ’, meaning ‘different’, because of the different notching degree of the external and adventive lobes.

Material examined

Holotype IRAN • Esfahan Province, Baghuk Mountain E section ; Hambast Formation; illustrated in Fig. 54A ; MB.C.30013 .

Paratypes IRAN • 2 specimens; Esfahan Province, Baghuk Mountain 1 section ; Hambast Formation; MB.C.30009 to MB.C.30010 • 1 specimen; Esfahan Province, Baghuk Mountain A section ; Hambast Formation; MB.C.30011 • 1 specimen; Esfahan Province, Baghuk Mountain B section ; Hambast Formation; MB.C.30012 • 2 specimens; Esfahan Province, Baghuk Mountain E section ; Hambast Formation; MB.C.30014 to MB.C.30015 • 2 specimens; Esfahan Province, Baghuk Mountain G section ; Hambast Formation; MB.C.30016 to MB.C.30017 .

Description

Holotype MB.C.30013 has a conch diameter of 90 mm and allows the study of three and a half volutions ( Fig. 54A ). Less than half of the last whorl belongs to the body chamber. The conch is very slender (ww/ dm =0.19) with a compressed whorl profile (ww/wh =0.55) that shows a concave venter bordered by an angular ventrolateral shoulder from the concave, converging flanks. One volution back, the compressed whorl profile is oval with rounded venter. The shell ornament does not change significantly during the last three volutions. It consists of fine, weakly sigmoidal ribs that are best visible on the inner flank and the ventrolateral margin, where they develop into weak nodes. These nodes disappear on the terminal body chamber.

The suture line of the holotype has a very narrow, parallel-sided and very deep (1.5 times of the adventive lobe) external lobe with very narrow, lanceolate and unsubdivided prongs. Both flanks of the inverted U-shaped ventrolateral saddle are parallel, and also the adventive and lateral lobes are parallel-sided. The adventive lobe has a semicircular base with eight small notches and the lateral lobe bears five notches ( Fig. 54B ).

Remarks

Lutites alius gen. et sp. nov. differs in the simple (non-subdivided prongs) and very deep external lobe from the other species of the genus. Furthermore, it lacks coarse ornament and possesses a very slender conch, which make a separation from other species easy.

Stratigraphic range

Upper part of the Hambast Formation; 1.70 to 1.20 m below the extinction horizon ( Lutites profundus Zone ).

Figures

Fig. 54. Lutites alius Korn & Hairapetian gen. et sp. nov. A. Lateral and dorsal view, holotype specimen MB.C.30013, section E, float. B. Suture line, specimen MB.C.30013, at 64.3 mm dm, 13.5 mm ww, 22.6 mm wh. Abbreviations: see Material and methods. Scale bar units =1 mm.