Anauchen crassus Gojšina, Hunyadi & Páll-Gergely, 2025

Anauchen crassus Gojšina, Hunyadi & Páll-Gergely sp. nov.

Figs 10 C View Figure 10 , 13 View Figure 13 , 14 View Figure 14 , 37 View Figure 37

Type material.

Holotype. Thailand • 1 empty shell (SH: 4.83 mm, SW: 3.54 mm); Ranong Province, south of Kra Buri, Tham Phra Kayang , southeastern part of the rock; 10°19.480'N, 98°45.933'E; 10 m a. s. l.; 22 Feb. 2015; A. Hunyadi leg.; CUMZ 14427 View Materials GoogleMaps . Paratypes. Thailand • 6 shells; same data as for holotype; coll. HA GoogleMaps .

Additional material examined.

Thailand • 1 shell (damaged, not paratype); same data as for holotype; coll. HA GoogleMaps .

Type locality.

Thailand, Ranong Province, south of Kra Buri, Tham Phra Kayang, southeastern part of the rock; 10°19.480'N, 98°45.933'E; 10 m a. s. l.

Diagnosis.

Anauchen species with finely dimpled (pasty) shell surface sculpture (no spiral striae), aperture adnate to last whorl, five strong apertural barriers (parietal, upper palatal, lower palatal, basal, columellar).

Description.

Shell conical, consisting of 5.5–6 thick-walled, regularly increasing, rounded, convex whorls separated by a moderately deep suture. All shells from the type material are somewhat weathered but colouration is dark reddish brown to pinkish, opaque. Protoconch weathered so the surface sculpture is not clear, not spirally striated, consisting of ~ 1.5–1.75 whorls, glossy and slightly darker than the rest of the shell. Teleoconch pasty, very finely radially striated, with no sign of spiral striation. Last whorl adnate to the penultimate and slightly descending near the aperture (~ 10 ° compared to the shell axis) making the aperture profile prosocline to the shell axis. Peristome continuous, leaning on the penultimate whorl at the parietal side in form of a thick and distinct callus. It is slightly paler in colour than the rest of the shell, expanded (particularly on the parietal side where it forms a distinct callus) but not reflected. Aperture equipped with five strong, high, relatively short, and thick barriers (parietal, upper palatal, lower palatal, basal, and columellar). Parietal lamella is the strongest in the aperture, blade-like, slightly oblique, its outer part curved towards the palatal side and only almost reaching the expanding peristome. Upper palatal and lower palatal plicae are similar, the lower one being stronger, more slender, higher, and positioned slightly deeper in the aperture. Basal plica small and very short, knob-like. Columellar lamella thick and horizontal, situated in the middle of the columellar wall. None of these barriers reach the expanding peristome. Surface of all apertural barriers is smooth. Sinulus wide and parabolic (due to the position of angular lamella and upper palatal plica). Umbilicus open and deep but moderately wide, measuring ~ 1 / 6 of the shell width. Only the penultimate whorl is visible through the umbilicus. A very short and shallow groove is present on the last ~ ¼ of the body whorl, running from the peristome towards the umbilicus.

Differential diagnosis.

This species is similar to Anauchen angthongensis Panha, 2002 from which it can be distinguished by the lack of spiral striation and much wider umbilicus. Additionally, A. crassus sp. nov. has a shallower suture resulting in less convex whorls than in A. angthongensis . Anauchen informis Vermeulen, Phung & Truong, 2007 is also spirally striated, has narrower umbilicus and its whorls are more convex and less regularly increasing. Anauchen banmiensis is spirally striated and has a shouldered last whorl. For differences from A. obesus sp. nov., see under that species. Boysidia phatangensis Dumrongrojwattana & Assawawattagee, 2018 is more slender and has more whorls which are more convex, with deeper sutures. It usually also has an additional lamella in the columellar-parietal boundary region, which was not (but may be) present in A. crassus sp. nov. Boysidia phatangensis has a bifid lamella (concrescent angular and parietal) on the parietal side while A. crassus sp. nov. has one blade-like lamella. Basal plica in B. phatangensis is seemingly more closely positioned to columellar lamella, while that of A. crassus sp. nov. is somewhere between the lower palatal and columellar or even closer to the lower palatal. Infraparietal lamella is absent in the new species, but present in B. phatangensis . Lastly, the umbilicus of B. phatangensis is slightly more excentrical and wider than in A. crassus sp. nov.

Measurements

(in mm, n = 5). SH = 4.83–5.39; SW = 3.54–4.04; AH = 2.15–2.24; 2.04–2.23.

Etymology.

The specific epithet refers to the thick (Lat. crassus) shell and apertural barriers of this species.

Distribution.

Only known from the type locality.