Liroceras leptum, Korn & Hairapetian, 2025

Liroceras leptum sp. nov.

urn:lsid:zoobank.org:act:

Fig. 25 View Fig ; Table 19 View Table19

Diagnosis

Species of Liroceras with thinly pachyconic, subinvolute conch (ww/dm ~ 0.68; uw/dm ~ 0.17), moderately depressed whorl profile (ww/wh ~1.45) and very high coiling rate (WER ~2.30) at a conch diameter of 40 mm. Whorl profile with broadly arched venter and flanks, broadly rounded umbilical margin, convex umbilical wall and moderately deep imprint zone ( IZR ~0.28). Without sculpture. Suture line with very shallow and wide external, lateral and umbilical lobes.

Etymology

From Greek ‘λεπτός’= ‘small, weak’; because of the rather small-sizes material.

Type material

Holotype

IRAN – Esfahan Province • Baghuk Mountain ; Hambast Formation, Vedioceras beds ( late Wuchiapingian); 2011; Korn et al. leg.; illustrated in Fig. 25 View Fig ; MB.C.32138 .

Paratypes

IRAN – Esfahan Province • 2 specimens; same data as for holotype; 2010; Korn et al. leg.; MB.C.32139, MB.C.32140.

Description

The best-preserved specimen is the obliquely deformed small holotype MB.C.32138 with a conch diameter of 41 mm ( Fig. 25B View Fig ). The conch geometry can only be reconstructed. According to this, the conch is thinly pachyconic and subinvolute (ww/dm=0.68; uw/dm=0.17) with a very high coiling rate (WER =2.31) and a moderately wide whorl overlap ( IZR = 0.28). The whorl profile is weakly depressed (ww/wh =1.44) with a broadly convex venter that merges continuously with the flanks the flanks. The umbilical margin is broadly rounded and the umbilical wall is convex ( Fig. 25A View Fig ). The suture line is nearly straight and shows very broad and shallow lobes on the area consisting of venter and flanks and the umbilical wall ( Fig. 25C View Fig ).

Remarks

The material of the new species does not show whether the umbilical extensions characteristic of the genus was present in the adult stage; therefore, assignment to Liroceras is not entirely certain. L. leptum sp. nov. differs from the other Late Permian species of the genus in the opened umbilicus and the slenderer conch; ww/dm ratio for a conch diameter of 40–50 mm is below a value of 0.70, but in the other species it is above 0.80.