Peripetoceras parum, Korn & Ghaderi, 2025

Korn, Dieter & Ghaderi, Abbas, 2025, Late Permian nautiloids from Julfa (NW Iran), European Journal of Taxonomy 1018, pp. 1-113 : 91-92

Peripetoceras parum sp. nov.

urn:lsid:zoobank.org:act:

Fig. 45 ; Table 27

Diagnosis

Species of Peripetoceras with thickly pachyconic, subinvolute conch (ww/dm ~ 0.75; uw/dm ~ 0.15), weakly depressed whorl profile (ww/wh ~1.45) and extremely high coiling rate (WER ~2.65) at a conch diameter of 70 mm. Whorl profile rounded rectangular with flatly arched venter and flanks, broadly rounded ventrolateral shoulder and umbilical margin, convex umbilical wall and a moderately deep imprint zone ( IZR ~0.25). Suture line with extremely shallow external and lateral lobe.

Etymology

From the Latin ‘ parum ’ (adjective, n.)= ‘even’; because of the nearly straight suture line.

Type material

Holotype

IRAN – West Azerbaijan • Aras Valley; Vedioceras Beds of the Julfa Formation ( late Wuchiapingian); 2011; Korn et al. leg.; illustrated in Fig. 45 ; MB.C.32072 .

Paratype

IRAN – West Azerbaijan • 1 specimen; same data as for holotype; 2018; Ghaderi leg.; MB.C.32073 .

Description

Holotype MB.C.32072 is a fairly complete but corroded specimen with a conch diameter of 70 mm ( Fig. 45B ). It is thickly pachyconic and subinvolute (ww/dm = 0.77; uw/dm = 0.16). The conch is expanding rapidly and has a very high coiling rate (WER = 2.67). On the last volution there are some changes in the shape of the whorl profile observable: while the cross section at the beginning of the last whorl is rather circular, at the end it is depressed (ww/wh= 1.44) with a flattened venter and slightly flattened flanks. The ventrolateral shoulder is rounded, as is the umbilical margin; the umbilical wall is steep and slightly flattened ( Fig. 45A ). The suture line extends with shallow undulation and possesses very shallow external and lateral lobes ( Fig. 45C ).

Remarks

Peripetoceras parum sp. nov. differs from the other Late Permian species of the genus in its general conch shape. Peripetoceras comploji and P. gigas are stouter and narrower umbilicate (ww/dm ~ 0.85; uw/dm ~0.10) than P. parum (ww/dm ~0.75; uw/dm ~0.15). However, it should be noted that the first two species were described from very large specimens, approximately twice the size of the holotype of P. parum . Peripetoceras freieslebeni has a slenderer conch (ww/dm ~ 0.65) than P. parum .

The two Roadian species P. ideliense and P. burovi have a significantly larger umbilicus (uw/dm ~0.30) than P. parum sp. nov. Of the Kungurian species P. wanneri and P. brouweri , the former is slenderer (ww/dm ~0.70) and the latter is stouter (ww/dm ~ 0.85). Peripetoceras parum sp. nov. also differs from P. wanneri in having a much more rounded ventrolateral shoulder and less clearly flattened flanks and venter.

Figures

Fig. 45. Peripetoceras parum sp. nov., holotype MB.C.32072 (Korn et al. 2011 Coll.) from the Vedioceras Beds of the Julfa Formation at Aras Valley. A. Reconstruction of apertural view. B. Lateral view. C. Suture line at dm =70.0 mm, ww =39.3 mm, wh= 26.8 mm. Scale bar units =1 mm.

Tables

Table 27. Conch dimensions (in mm) and ratios of Peripetoceras parum sp. nov.

Nr.	dm	ww	wh	uw	ah	ww/dm	ww/wh	uw/dm	WER	IZR
MB.C.32072	70.4	53.9	37.4	11.2	27.3	0.77	1.44	0.16	2.67	0.27
MB.C.32072	43.1	36.7	22.2	6.9	–	0.85	1.65	0.16	–	–