Liroceras choopani, Korn & Ghaderi, 2025

Korn, Dieter & Ghaderi, Abbas, 2025, Late Permian nautiloids from Julfa (NW Iran), European Journal of Taxonomy 1018, pp. 1-113 : 84-87

Liroceras choopani sp. nov.

urn:lsid:zoobank.org:act:

Figs 41–42 ; Table 24

Liroceras sp. indet. – Teichert et al. 1973: 401, pl. 8 fig. 9.

Liroceras sp. – Gliwa et al. 2020: text-fig. 17e.

Diagnosis

Species of Liroceras with thinly globular, involute conch (ww/dm ~ 0.85–0.90; uw/dm ~ 0.05), moderately depressed whorl profile (ww/wh ~ 1.50–1.65) and high to very high coiling rate (WER ~ 2.00–2.35) between a conch diameter of 75 and 135 mm. Whorl profile with broadly arched venter and flanks, broadly rounded umbilical margin and convex umbilical wall and deep imprint zone ( IZR ~ 0.40). Ornament with coarse, convex growth lines and coarse spiral lines. Suture line nearly straight.

Etymology

Named after Hadi Choopan, former Iranian Mr Olympia, referring to the most robust nautiloid found in the Julfa assemblage.

Type material

Holotype

IRAN – East Azerbaijan • Zal; Araxoceras Beds of the Julfa Formation ( early Wuchiapingian); 2018; Ghaderi leg.; illustrated in Fig. 41A ; MB.C.32067 .

Paratypes

IRAN – East Azerbaijan • 1 specimen; same data as for holotype; illustrated in Fig. 41B–C ; MB.C.32068 • 1 specimen; Ali Bashi 4; Araxoceras Beds of the Julfa Formation ( early Wuchiapingian); 2018; Ghaderi leg.; MB.C.32069 • 1 specimen; same data as for holotype; 2010; Korn et al. leg.; MB.C.32070 • 1 specimen; Ali Bashi ; Araxoceras Beds of the Julfa Formation ( early Wuchiapingian); illustrated in Fig. 42 ; GLM #GH1005. – West Azerbaijan • 1 specimen; Aras Valley; Araxoceras Beds of the Julfa Formation ( early Wuchiapingian); 2013; Korn et al. leg.; illustrated in Fig. 41D–E ; MB.C.29350.

Description

Holotype MB.C.32067 is an incomplete specimen with a conch diameter of approximately 133 mm ( Fig. 41A ). The proportions of the conch can only be estimated; the specimen was apparently globular (ww/dm ~ 0.90) with an almost closed umbilicus and a moderately high coiling rate (WER ~ 2.10). The whorl profile is semilunate and widest at the broadly rounded umbilical margin; it has a deep imprint zone ( IZR ~0.40). Flanks and venter are continuously rounded to form a hemisphere. Shell remains show very coarse growth lines, which extend with a convex arch across the flanks and form a deep, subangular ventral sinus. A second element of ornament are coarse spiral lines, which are almost of the same strength as the growth lines, together forming a reticulated ornament.

Paratype MB.C.32068 with a conch diameter of 112 mm was sectioned for studying the conch ontogeny ( Fig. 41B ), but the inner whorls are recrystallised or deformed. However, it shows an almost isometric ontogeny between 48 and 113 mm diameter. During this interval of one and a half volutions, the conch changes from thickly pachyconic (ww/dm =0.82 at 48.5 mm dm) to thinly globular (ww/dm = 0.87 at 113 mm dm). The umbilicus is almost closed (uw/dm decreases from 0.06 to 0.02). The suture line of the specimen is almost straight with a very shallow external lobe and an also very shallow lateral lobe ( Fig. 41C ).

The smaller fragmentary paratype MB.C.29350 with a conch diameter of 50 mm had to be reconstructed for its conch proportions ( Fig. 41E ), but it is evident that it is slightly slenderer than the two large specimens (ww/dm ~0.78). This specimen is preserved with shell material that shows rhythmically reinforced growth lines extending with a broadly rounded lateral projection and a deep subangular ventral sinus.

Remarks

Liroceras choopani sp. nov. is one of the few species in the species-rich genus with an almost closed umbilicus and is therefore easy to distinguish from many other species, which usually have a uw/ dm ratio of about 0.20. Among the Middle and Late Permian species with a nearly closed umbilicus, L. meishanense and L. hsuechuechiani (Chao, 1854) are slender (ww/dm ~0.57 and 0.67, respectively), L. gardenense and L. didmyoaurise are stouter (ww/dm> 0.90) at comparable conch diameters.

Large specimens of L. choopani sp. nov. have a coarser ornamentation consisting of growth lines and spiral lines. Such an adult ornament is not known from other species, although only a few species with a conch diameter of over 100 mm are known.

Figures

Fig. 41 (opposite page). Liroceras choopani sp. nov. from the Araxoceras Beds of the Julfa Formation. A. Holotype MB.C.32067 (Ghaderi 2018 Coll.) from Zal, lateral and apertural views with dorsal view reconstruction. B. Paratype MB.C.32068 (Ghaderi 2018 Coll.) from Zal, cross section. C. The same specimen, suture line at ww=84.5 mm. D. Paratype MB.C.29350 (Korn et al. 2013 Coll.) from Aras Valley, lateral and ventral views. E. The same specimen; reconstruction of apertural view. Scale bar units=1 mm.

Fig. 42. Liroceras choopani sp. nov., paratype GLM#GH1005 from the Araxoceras Beds of the Julfa Formation from Julfa, dorsal and lateral views. Scale bar units= 1 mm.

Tables

Table 24. Conch dimensions (in mm) and ratios of Liroceras choopani sp. nov.; reconstructed dimensions and ratios in italics.

Nr.	dm	ww	wh	uw	ah	ww/dm	ww/wh	uw/dm	WER	IZR
MB.C.32067	133.0	118.0	71.0	7.0	41.0	0.89	1.66	0.05	2.09	0.42
MB.C.32068	113.0	98.2	66.5	2.5	38.8	0.87	1.48	0.02	2.32	0.42
MB.C.32068	74.2	66.4	44.0	3.3	25.7	0.89	1.51	0.04	2.34	0.42
MB.C.32068	48.5	39.7	26.9	2.9	–	0.82	1.48	0.06	–	–
MB.C.29350	49.5	38.5	28.0	1.0	17.0	0.78	1.38	0.02	2.32	0.39