Clivotirolites petilus 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 : 66-67

Clivotirolites petilus Korn & Hairapetian gen. et sp. nov.

urn:lsid:zoobank.org:act:6608C3B9-8B98-4E05-91E6-DA463119748F

Fig. 44 ; Table 21

Diagnosis

Species of Clivotirolites gen. nov. with conch reaching 120 mm dm. Subadult stage with trapezoidal, weakly compressed whorl profile (ww/wh=0.90) and flattened tectiform; 15 coarse ventrolateral nodes per volution. Adult stage with trapezoidal, weakly compressed whorl profile (ww/wh =0.70), flat venter and angular ventrolateral shoulder; weak ribs and ventrolateral nodes. Prongs of external lobe bifid; altogether 16 notches of E, A and L lobes.

Etymology

From the Latin ‘ petilus ’, meaning ‘slim’, because of the slender conch.

Material examined

Holotype IRAN • Esfahan Province, Baghuk Mountain E section ; Hambast Formation; illustrated in Fig. 44A ; MB.C.29962 .

Description

Holotype MB.C.29962 is a comparatively well-preserved individual with 80 mm conch diameter and allows the study of two whorls ( Fig. 44A ). Nearly three quarters of the last volution belong to the body chamber. The adult whorl profile is compressed (ww/wh ~ 0.80) and weakly trapezoidal with gently diverging flanks, a subangular ventrolateral shoulder and a flattened but still weakly rounded venter. The sculpture of the last phragmocone volution has 15 coarse ventrolateral nodes. With beginning of the terminal body chamber, these nodes become weaker and more numerous; at the end of the body chamber, ten faint nodes occur in a quarter of a volution.

The suture line of the holotype has an external lobe with weakly converging flanks. Its prongs are slightly pouched and possess three denticles. The ventrolateral saddle is inflated and followed by an asymmetric, pouched adventive lobe with oblique, weakly rounded base and seven small notches. The lateral lobe is generally V-shaped with weakly diverging flanks; it has six notches ( Fig. 44B ).

Remarks

Clivotirolites petilus gen. et sp. nov. differs in the lower number (about 15 per volution) of ventrolateral nodes from the species of Clivotirolites decorates gen. et sp. nov.

Stratigraphic range

The single specimen was collected from float of the upper part of the Hambast Formation.

Figures

Fig. 44. Clivotirolites petilus Korn & Hairapetian gen. et sp. nov. A. Lateral and dorsal view, holotype MB.C.29962, section E, float. B. Suture line, holotype MB.C.29962, at 45.5 mm dm, 14.9 mm wh. Abbreviations: see Material and methods. Scale bar units=1 mm.