Permodomatoceras hamdii sp. nov.

urn:lsid:zoobank.org:act: C3FB68E4-18D0-4B64-946A-75FE355723EA

Fig. 11; Table 3

Domatoceras hunicum – Shimansky 1965b: 161, pl. 15 fig. 12. — Teichert & Kummel 1973: 421, pl. 1 figs 7–8, pl. 2 figs 3–4.

Diagnosis

Species of Permodomatoceras with extremely discoidal, subevolute conch (ww/dm ~ 0.30; uw/dm ~ 0.40), weakly compressed whorl profile (ww/wh ~ 0.80) and very high coiling rate (WER ~ 2.45) at a conch diameter of 80 mm. Whorl profile with weakly concave venter, subangular ventrolateral shoulder, gently convergent, flattened flanks and narrowly rounded umbilical margin. Ornament with fine growth lines, without ribs or nodes. Suture line with a narrow and very shallow external lobe and a much larger and deeper, broadly rounded lateral lobe.

Etymology

Named after the late Bahaeddin Hamdi (1935–2019), the promoter of palaeontology in Iran.

Type material

Holotype

IRAN – East Azerbaijan • Ali Bashi 4; Araxoceras Beds of the Julfa Formation (early Wuchiapingian); 2018; Ghaderi leg.; illustrated in Fig. 11; MB.C.32006.

Paratypes

IRAN – West Azerbaijan • 1 specimen; Aras Valley; Araxoceras Beds of the Julfa Formation (early Wuchiapingian); 2018; Ghaderi leg.; MB.C.32007 • 1 specimen; same data as for preceding; 2011; Korn et al. leg.; MB.C.32008 • 1 specimen; same data as for preceding; 2013; Korn et al. leg.; MB.C.32009 • 2 specimens; same data as for preceding; 2018; Korn et al. leg.; MB.C.32010 to MB.C.32011. – East Azerbaijan • 1 specimen; Ali Bashi 4; Araxoceras Beds of the Julfa Formation (early Wuchiapingian); 2018; Ghaderi leg.; MB.C.32012 • 1 specimen; same data as for preceding; 2010; Korn et al. leg.; MB.C.32013 • 1 specimen; same data as for preceding; 2011; Korn et al. leg.; MB.C.32014 • 1 specimen; Zal; Araxoceras Beds of the Julfa Formation (early Wuchiapingian); 2018; Ghaderi leg.; MB.C.32015.

Description

Holotype MB.C.32006 is a phragmocone fragment with a whorl height of 30 mm (Fig. 11A) and allows for examination of the dorsal whorl area. The shape of the conch was reconstructed using this fragment; this results in a diameter of 80 mm. The whorl profile of the specimen is compressed (ww/wh=0.80) and trapezoidal with a very weakly concave venter, subangular ventrolateral shoulders, flattened and convergent flanks, a rounded umbilical margin and a very shallow dorsal zone (Fig. 11B). The dorsal zone shows that the penultimate whorl also had a weakly concave venter. The complete suture line is exposed. It shows that the external lobe is very shallow and that the ventrolateral saddle is subangular. The lateral lobe is broadly rounded and continues, at the umbilical seam, into a very shallow internal lobe, in which a very low and rounded saddle is raised (Fig. 11C). The septa are closely spaced; there are about ten chambers on a quarter of a volution (SD ~9 degrees).

Some of the other specimens, such as paratype MB.C.32015, which is not illustrated, show a transformation of the ventrolateral shoulder from a subangular to a tightly rounded shape in the adult stage. In this specimen the shape change takes place at about 28 mm whorl height.

Remarks

It is most likely that the specimens illustrated by Shimansky (1965b) and Teichert & Kummel (1973) under the name “ Domatoceras hunicum ” belong to this species. However, P. hunicum differs from the new species in having septa in much larger distances (about five septa per quarter volution) than P. hamdii sp. nov. (10 septa per quarter volution). Another difference is the rate on whorl overlap, which is rather great in P. hunicum (IZR ~ 0.15), while it is very low in P. hamdii (IZR ~ 0.05).

The new species has a narrower whorl profile (ww/wh = 0.80) than the type species of the genus. However, as its conch shape with the almost rectangular, rather wide whorl profile clearly distinguishes it from the species of the genus Domatoceras, it is classified here as Permodomatoceras.