Domatoceras convergens ( Abich, 1878 )

Korn, Dieter & Ghaderi, Abbas, 2025, Late Permian nautiloids from Julfa (NW Iran), European Journal of Taxonomy 1018, pp. 1-113 : 18

Domatoceras convergens ( Abich, 1878)

Fig. 10

Nautilus convergens Abich, 1878: 17 , pl. 3 fig. 2.

Domatoceras convergens – Shimansky 1965a: 41, pl. 15 fig. 9.

Diagnosis

Species of Domatoceras with extremely discoidal, subevolute and weakly compressed, inverted trapezoidal whorl profile (ww/wh ~0.60) at a conch diameter of 75 mm. Whorl profile with flat, very narrow venter, subangular ventrolateral shoulder, convergent, flattened flanks and broadly rounded umbilical margin. Suture line with a very narrow and very shallow external lobe and a much larger and deeper, broadly rounded lateral lobe.

Material examined

IRAN – West Azerbaijan • 1 specimen; Aras Valley; Araxoceras Beds of the Julfa Formation ( early Wuchiapingian); 2018; Ghaderi leg.; illustrated in Fig. 10 ; MB.C.32003 • 1 specimen; same data as for preceding; 2018; Ghaderi leg.; MB.C.32004 . – East Azerbaijan • 1 specimen; Ali Bashi 4; Araxoceras Beds of the Julfa Formation ( early Wuchiapingian); 2010; Korn et al. leg.; MB.C.32005 .

Description

Specimen MB.C.32003 is, though fragmentarily preserved, suitable for identification as it shows some specific characters ( Fig. 10A ). It has a whorl height of 26 mm and a ww/wh ratio of 0.57. The venter is flat and bordered by an angular ventrolateral shoulder; the flanks are weakly convex and converge from the rounded umbilical margin ( Fig. 10B ). The suture line shows a small and very shallow external lobe and a very wide, broadly rounded lateral lobe ( Fig. 10C ).

Remarks

Abich (1878: 17, pl. 3 fig. 2) described and illustrated, as “ Nautilus convergens , nov. form.”, a fragment (less than a quarter of a volution) of an internal mould of 40 mm whorl height. From this, the conch shape can be reconstructed rather well. The inverted trapezoidal whorl profile is compressed (ww/wh =0.62) and very weakly inflected dorsally by the preceding whorl. It is widest near the umbilical margin. The flanks converge rather rapidly and are separated from the flattened venter by a subangular ventrolateral shoulder. There is a shallow longitudinal groove on the outer portion of the flank just adjacent to the ventrolateral shoulder. No ornament can be seen. The suture line shows a broad rounded lobe on the flank and a very shallow lobe on the venter.

Figures

Fig. 10. Domatoceras convergens (Abich, 1878), specimen MB.C.32003 (Ghaderi 2018 Coll.) from the Araxoceras Beds of the Julfa Formation at Aras Valley. A. Lateral view. B. Whorl profile. C. Suture line at ww =14.5 mm, wh=26.0 mm. Scale bar units =1 mm.