Tardunautilus minor, Korn & Ghaderi, 2025

Tardunautilus minor gen. et sp. nov.

urn:lsid:zoobank.org:act:

Fig. 32 View Fig ; Table 18 View Table 18

Diagnosis

Species of Tardunautilus gen. nov. with thinly discoidal, evolute conch (ww/dm ~0.40; uw/dm ~ 0.47), weakly depressed whorl profile (ww/wh ~ 1.40) and moderately high coiling rate (WER ~ 1.85) at a conch diameter of 70 mm. Whorl profile rounded triangular with strongly divergent flanks; venter broadly rounded, area of flanks and umbilical wall flattened. Sculpture with one row of ventrolateral nodes in the intermediate growth stage. Suture line with a broad and shallow external lobe, and a broadly rounded lateral lobe.

Etymology

From the Latin ‘ minor ’ (noun) =‘the smaller’; because of the small size of the conch.

Type material

Holotype

IRAN – East Azerbaijan • Kuh-e-Ali Bashi ; Araxoceras Beds of the Julfa Formation ( early Wuchiapingian); 2011; Korn et al. leg.; illustrated in Fig. 32 View Fig ; MB.C.32058 .

Description

Holotype MB.C.32058 is a whorl segment of about 120 degrees and consists of the last phragmocone chamber and a longer part of the body chamber ( Fig. 32B View Fig ). The diameter of the evolute specimen may have been about 72 mm. The depressed whorl profile (ww/wh = 1.42) has a triangular outline with a broadly arched venter and a rounded ventrolateral shoulder from which the flattened flanks converge towards the umbilical seam. The imprint zone is very small ( Fig. 32A View Fig ).

In the whorl segment, there are eight conical nodes located on the ventrolateral shoulder. The suture line shows a wide and shallow external lobe, a broadly rounded ventrolateral saddle and a broadly rounded lateral lobe, which is slightly smaller than the external lobe ( Fig. 32C View Fig ).

Remarks

Tardunautilus minor gen. et sp. nov. differs from T. nimius gen. et sp. nov. in the presence of only one row of conical nodes on the ventrolateral shoulder, while T. nimius has two rows, which are located on the outer flank and the ventrolateral shoulder. Furthermore, the whorl profile is much less depressed in T. minor (ww/wh ~1.50) than in T. nimius (ww/wh ~ 1.80).