Celeroliroceras celere, Korn & Ghaderi, 2025

Korn, Dieter & Ghaderi, Abbas, 2025, Late Permian nautiloids from Julfa (NW Iran), European Journal of Taxonomy 1018, pp. 1-113 : 88-89

Celeroliroceras celere gen. et sp. nov.

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Fig. 43 ; Table 25

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

Diagnosis

Species of Celeroliroceras gen. nov. with thinly globular, subinvolute to involute conch (ww/dm ~ 0.85–0.90; uw/dm ~ 0.15), weakly to moderately depressed whorl profile (ww/wh ~1.40–1.60) and extraordinarily high coiling rate (WER ~3.60) between a conch diameter of 30 and 60 mm. Whorl profile with broadly arched venter and flanks, broadly rounded umbilical margin and convex umbilical wall and small imprint zone ( IZR ~0.15). Shell surface smooths. Suture line nearly straight.

Etymology

From the Latin ‘ celere ’ (adjective, n.)=‘fast’; because of the conch geometry with the extraordinarily high coiling rate.

Type material

Holotype

IRAN – West Azerbaijan • Aras Valley; Araxoceras Beds of the Julfa Formation ( early Wuchiapingian); 2011; Korn et al. leg.; illustrated in Fig. 43 ; MB.C.29352 .

Description

Holotype MB.C.29352 is fully septate with a conch diameter of 57 mm ( Fig. 43A ). It is slightly deformed but relatively well preserved, allowing the study of conch geometry, suture line and, with limitations, ornamentation. The remarkable conch geometry is mainly caused by the extraordinarily high coiling rate (WER =3.60). The conch is globular and involute (ww/dm =0.88; uw/dm=0.14) and the ww/wh ration amounts 1.60. The whorl profile is crescent-shaped with a convex umbilical wall and a rounded umbilical margin from which the flanks converge strongly towards the broadly rounded venter ( Fig. 43B ). The whorl overlap zone is very small ( IZR = 0.15). It appears that the whorl width increases faster than the whorl height on the last volution; the ww/wh ratio increases from 1.43 to 1.60 during the last half volution.

There are some shell remains attached to the phragmocone; these are almost smooth with no traces of ornamentation. The suture line is almost straight, but has a very flat and very wide external lobe ( Fig. 43C ).

Remarks

Celeroliroceras celere gen. et sp. nov. is very different from all other Late Permian nautiloids. It is clearly separable from the co-occurring Liroceras choopani sp. nov. by its extraordinarily high coiling rate (WER= 3.60 in contrast to 2.30 in L. choopani ) and the much smaller whorl overlap rate.

Figures

Fig. 43. Celeroliroceras celere gen. et sp. nov., holotype MB.C.29352 (Korn et al. 2011 Coll.) from the Araxoceras Beds of the Julfa Formation at Aras Valley. A. Lateral and apertural views. B. Reconstruction of apertural view. C. Suture line at dm= 57.0 mm, ww = 46.5 mm, wh= 27.2 mm. Scale bar units = 1 mm.

Tables

Table 25. Conch dimensions (in mm) and ratios of Celeroliroceras celere gen. et sp. nov.

Nr.	dm	ww	wh	uw	ah	ww/dm	ww/wh	uw/dm	WER	IZR
MB.C.29352	57.1	50.5	31.6	7.8	27.0	0.88	1.60	0.14	3.60	0.15
MB.C.29352	32.6	28.5	19.9	5.7	–	0.87	1.43	0.17	–	–