Happia decaensi Gargominy, 2025

Happia decaensi Gargominy sp. nov.

Fig. 20 View Figure 20

Type locality.

French Guiana, Camopi, Mont Itoupé.

Type material.

Holotype. French Guiana • 1 95 % ethanol specimen (shell separated); Camopi, Mont Itoupé ; 3.02696 ° N, 53.07902 ° W; alt. 800 m; 06 Jan. 2016 – 17 Jan. 2016; Thibaud Decaëns, Sébastien Cally leg.; MNHN-IM-2013-75995 GoogleMaps . Paratypes (7). French Guiana • 4 dry specimens; Régina, RN des Nouragues, carré J 12 du km 2 layonné (N 3) ; 4.0883 ° N, 52.67675 ° W; alt. 80 m; 04 Nov. 1997; TR, OG leg.; forêt primaire, pied d’arbre à contrefort (code J- 12-22); MNHN -IM-2018-14023 , MNHN -IM-2018-14429 , MNHN -IM-2018-14430 , MNHN -IM-2018-14431 GoogleMaps • 1 dry specimen; Régina, RN des Nouragues, carré G 12 du km 2 layonné (N 16) ; 4.09011 ° N, 52.67922 ° W; alt. 80 m; 16 Nov. 1997; TR, OG leg.; forêt primaire, bord de Crique Couac (rive droite); MNHN -IM-2018-14024 GoogleMaps • 2 dry specimens; Régina, RN des Nouragues, carré I 17 du km 2 layonné (N 17) ; 4.08535 ° N, 52.67996 ° W; alt. 73 m; 17 Nov. 1997; TR, OG leg.; confluence crique Nouragues et crique Moteur, forêt primaire, accumulation de bois pourri; MNHN -IM-2018-14022 , MNHN -IM-2018-14428 GoogleMaps .

Diagnosis.

A large Happia species with relatively high whorls, strong indentation on the upper sutural margin, largely umbilicated.

Description.

Holotype. Shell small (height 2.8 mm, greater diameter 5.6 mm), dextral, totally depressed, thin; colour pale corneous; whorls 3.8, inflated, rounded, slightly flattened on the upper part, overlapping the preceding, separated by a marked suture; spire planispiral, coiling rapidly increasing. Protoconch 1.7 whorl, with ~ 10 delicate spiral threads hardly visible due to periostracal erosion, also visible from adapical view; protoconch / teleoconch transition distinct, particularly from adapical view; teleoconch smooth (but see remarks below), with sigmoid, prominent, closely spaced growth wrinkles with irregular levels of shell calcification underneath, radial on umbilical part of whorls, strongly rounded backwards near upper suture. Body whorl rounded, strongly flattened above periphery up to a small bulge above the suture. Aperture prosocline, strongly sigmoid with an acute and deep (1 mm) incision in parietal angle, basally circular. Peristome simple, sharp. Umbilicus very large, almost half of the greater diameter, conical with flat protoconch entirely visible.

Etymology.

The species is named after Thibaud Decaëns who provided the holotype and only living specimen, a good friend and experienced earthworm expert.

Distribution.

This species is known from French Guiana only, Nouragues and Itoupé.

Habitat.

Leaf litter of tropical rain forest, from 80 (Nouragues) to 800 m (Itoupé) a. s. l.

Remarks.

The holotype was barcoded, without success.

The paratype MNHN -IM-2018-14022 is a juvenile (2.7 whorls) and distinctly shows the spiral rows of minute papillae on the protoconch; this spiral micro-sculpture is also visible on the complete teleoconch which argues for its attribution to genus Happia ( Baker 1925: pl. 8 fig. 35; Roosen and Breure 2024). Paratype MNHN -IM-2018-14429 (3.7 whorls) also shows this spiral micro-sculpture on the umbilical part of the teleoconch whorls, thus appearing reticulate when crossed with the marked growth lines (Fig. 20 E View Figure 20 ’).

Referring to Roosen and Breure (2024), the new species is the largest of the genus. The type species Happia ammonoceras (L. Pfeiffer, 1855) (syntype NHMUK 20210342) from Colombia is smaller, flatter, the body whorl more inflated. Drepanostomella pinchoti Pilsbry, 1930 (holotype ANSP 152648) described from Panama and recorded from Venezuela ( Thompson 1957) is smaller with the umbilicus only 1 / 3 of the diameter. When compared to a juvenile of the new species (of the same size), it is more discoid and flatter.

This new species represents the first record of the genus Happia in French Guiana.