Trocholites vortex, Aubrechtová & Korn, 2025

Trocholites vortex sp. nov.

urn:lsid:zoobank.org:act:115DF999-F5D6-4FE3-8853-72A8F451CC7C

Fig. 26 View Fig ; Table 17 View Table 17

Diagnosis

Species of the genus Trocholites with an adult conch diameter of about 50 mm. Conch in the last whorl thickly discoidal (CWI ~ 0.47) and evolute (UWI ~ 0.46) with moderately high coiling rate (WER ~ 1.80). Whorl profile weakly depressed (WWI ~ 1.45), rounded, moderately embracing (IZR ~ 0.20). Shell ornament with growth lines or extremely fine, regularly spaced lirae; venter and outer flanks with thin and irregularly spaced annuli or raised lirae. Phragmocone chambers long in all growth stages (RCL ~ 0.45). Suture line nearly straight.

Etymology

From the Latin ‘ vortex ʼ (nomen) = ‘a whirl’, referring to the perfectly spiral shape of the holotype.

Type material

Holotype

GERMANY – Mecklenburg-Vorpommern • Parchim; Lasnamägi or Uhaku regional stages ; 1969; Helms Coll.; illustrated in Fig. 26 View Fig ; MB.C. 22574 .

Description

Holotype MB.C.22574 ( Fig. 26 View Fig ) is a nearly complete conch with 49 mm diameter and is composed of five whorls; the initial chamber has probably not been preserved. The body chamber is preserved in length of about 230 degrees, but does not have the terminal aperture preserved. In the last half volution, the conch proportions change only slightly; the conch becomes more thickly discoidal (CWI changes from 0.45 to 0.47), less evolute (UWI decreases from 0.48 to 0.45) and the whorl profile becomes less depressed (WWI decreases from 1.52 to 1.45). The last whorl is moderately impressed (IZR = 0.19) and moderately expanding (WER= 1.80). The venter of the body chamber has two longitudinal grooves separated by a single ridge. The shell ornament consists of growth lines or extremely fine, regularly spaced lirae. On the venter and outer flanks, there are thin and irregularly spaced annuli or raised lirae. The phragmocone chambers are long (RCL = 0.47); the suture line is almost straight.

Remarks

Compared to representatives of other species of Trocholites , the holotype of T. vortex sp. nov. has a large conch diameter of about 50 mm. This may not yet represent the adult stage as there is no evidence of the terminal aperture and the rate of growth of the body chamber height and width does hardly change. In addition, the last phragmocone chambers are not shortened.

Some specimens of Trocholites hospes attain comparatively large adult conch diameters, but their conchs with diameters of around 50 mm are much stouter (CWI ~ 0.60 vs ~ 0.45 in T. vortex sp. nov. at 50 mm diameter) and more narrowly umbilicate (UWI ~ 0.35 vs ~ 0.45) with whorls more strongly impressed dorsally (IZR ~ 0.30 vs ~ 0.30).

Trocholites vortex sp. nov. differs from T. luna sp. nov. in adult size exceeding 50 mm, the higher coiling rate (WER = 1.80 vs 1.60), the wider adult body chamber (CWI = 0.47 vs 0.38), the less depressed whorl profile (WWI = 1.45 vs 1.56) and the narrower umbilicus (UWI = 0.45 vs 0.52).

Trocholites vortex sp. nov. also resembles T. vodickai sp. nov. in umbilical and whorl width, but T. vortex has a greater adult size (over 50 mm vs 40 mm) and the phragmocone chambers are longer (RCL = 0.30–0.40 in last whorl of T. vodickai ).

Compared to T. vortex sp. nov., the two specimens of T. kadakaensis sp. nov. are smaller in adult size, have a lower coiling rate (WER ~ 1.70 vs 1.80) and the whorl profile is more depressed at dm ~ 40 mm (WWI ~ 1.80 vs ~ 1.50).The specimens of T. depressus reach up to max. 40 mm diameter in adult size; they are generally more discoidal (CWI = 0.35–0.40 vs 0.47) with a much lower coiling rate (WER ~ 1.65 vs 1.80) and the ornament on inner whorls has ribs.