Tainoceras admonens, Korn & Ghaderi, 2025

Tainoceras admonens sp. nov.

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Fig. 34 View Fig ; Table 20 View Table 20

Tainoceras (?) sp. – Gliwa et al. 2020: text-fig. 17c.

Diagnosis

Species of Tainoceras with thinly pachyconic, subevolute conch (ww/dm ~ 0.65; uw/dm ~ 0.32), weakly depressed whorl profile (ww/wh ~ 1.45) and extremely high coiling rate (WER ~ 2.85) at a conch diameter of 50 mm. Whorl profile polygonal with convergent flanks; venter tectiform with broad longitudinal midventral groove, flanks weakly concave, umbilical margin narrowly rounded. Sculpture with about 12 faint ribs on the flank per volution, strengthened to form small, longitudinally elongated tubercles on the ventrolateral shoulder. Suture line with a shallow, tongue-shaped external lobe and a broadly rounded, very shallow lateral lobe.

Etymology

From the Latin ‘ admonens ’ (verb in participle)=‘reminding’; because of the similar conch geometry with the Late Carboniferous species of the genus.

Type material

Holotype

IRAN – West Azerbaijan • Aras Valley; Vedioceras Beds of the Julfa Formation ( late Wuchiapingian); 2011; Korn et al. leg.; illustrated in Fig. 34D–F View Fig ; MB.C.29348 .

Paratype

IRAN – West Azerbaijan • 1 specimen; same data as for holotype; illustrated in Fig. 34A–C View Fig ; MB.C.32060 .

Description

Holotype MB.C.29348 is a partly corroded specimen, but nevertheless allows examination of the conch geometry, sculpture and suture line ( Fig. 34D View Fig ). It has a conch diameter of 48 mm and is fully chambered. The conch is thinly pachyconic and subevolute (ww/dm =0.65; uw/dm =0.32) with an extremely high coiling rate (WER=2.80) and a very small whorl overlap zone. The whorl profile is weakly depressed whorl profile (ww/wh = 1.44) and polygonal with divergent, concave flanks; the umbilical margin is narrowly rounded and the umbilical wall is flattened. The ventrolateral shoulder is pronounced and subangular; it delimits the broad venter, which is rounded-tectiform in cross section and possesses three concave zones, of which the central is the deepest ( Fig. 34E View Fig ). The sculpture consists of faint, longitudinally elongated conical tubercles with a position on the ventrolateral shoulder. There are about 15 of such tubercles per volution. The venter bears one row of very low, blunt tubercles on each side adjacent to the longitudinal groove. These tubercles do not correspond to the riblets on the flank and are more numerous. The suture line is undulated with very shallow lobes in the concave parts of the conch ( Fig. 34F View Fig ).

Paratype MB.C.32060 is a rather strongly corroded specimen, but nevertheless allows examination of the conch geometry, sculpture and suture line. It has a conch diameter of 56 mm and is fully chambered ( Fig. 34A View Fig ). The conch is thinly pachyconic and subevolute (ww/dm = 0.67; uw/dm = 0.32) with an extremely high coiling rate (WER =2.89) and a very small whorl overlap zone. The whorl profile is moderately depressed whorl profile (ww/wh = 1.50) is generally rounded polygonal with slowly divergent, weakly concave flanks; the umbilical margin is narrowly rounded and the umbilical wall is flattened. The ventrolateral shoulder is pronounced and delimit the broad venter, which is convex in cross section, but possesses three concave zones, of which the central is the deepest ( Fig. 34B View Fig ). The sculpture consists of low, longitudinally elongated conical tubercles with a position on the ventrolateral shoulder. There are about 12 of such ribs per volution. The venter bears one row of very low, barely visible nodes on both sides of the longitudinal groove. The suture line is undulated with very shallow lobes in the concave parts of the conch ( Fig. 34C View Fig ).

Remarks

Tainoceras admonens sp. nov. has, because of its very weak sculpture, a marginal position in the morphological spectrum of the genus. Particularly the weak ribs on the flank and the presence of only one row of ventral nodes distinguishes the new species from the others of the genus.

The general conch shape and the sculpture are similar to the stratigraphically older species of the genus, such as the Late Carboniferous type species T. quadrangulum , but the new species differs in the considerably weaker developed ventrolateral and ventral tubercles. The Early Permian T. clydense is more similar, especially in the non-corresponding ventral and ventrolateral tubercles. However, the ventral nodes in T. clydense are much higher than in T. admonens sp. nov. In addition, the umbilicus in T. clydense is narrower (uw/dm ~0.25) than in T. admonens (uw/dm ~ 0.30).