Georissa insulae, Zacaery Khalik, Mohd, P. Hendriks, Kasper, J. Vermeulen, Jaap & Menno Schilthuizen,, 2019

Zacaery Khalik, Mohd, P. Hendriks, Kasper, J. Vermeulen, Jaap & Menno Schilthuizen,, 2019, Conchological and molecular analysis of the " non-scaly " Bornean Georissa with descriptions of three new species (Gastropoda, Neritimorpha, Hydrocenidae), ZooKeys 840, pp. 35-86 : 59-62

Georissa insulae sp. n. Figure 14 A–K

Georissa williamsi Godwin-Austen: Clements et al. 2008: Appendix D; Phung et al. (2017), fig. 8C.

Type locality.

Pulau Mantanani Besar, Sabah, Malaysia (06°43.06'N, 116°20.50'E).

Type material.

Holotype. Pulau Mantanani Besar, Sabah, Malaysia (06°43.06'N, 116°20.50'E): MZU/MOL 18.01 (Fig. 14 A–C). Paratypes: Pulau Mantanani Besar, Sabah, Malaysia (06°43.06'N, 116°20.50'E): MZU/MOL 18.02 (Fig. 14 D–K). Pulau Mantanani Besar, West Coast Province, Sabah: JJV 9845 (8), JJV 9860 (>50), BOR/MOL 3718, BOR/MOL 7161 (1), BOR/MOL 7174 (9). Pulau Lungisan, Sabah: BOR/MOL 3744. Kinabalu N.P., Poring Hot Springs, along path to waterfall, West Coast Province, Sabah: JJV 13003 (1). Gua Mundau, Pitas, Sabah (06°33.02'N, 116°52.07'E): BOR/MOL 4373 (1, broken shell).

Etymology.

The name is a genitive singular of the Latin word insula, meaning ‘island’, which refers to the Mantanani islands, the main collecting locality.

Description.

Protoconch. Colour: orange. Sculpture pattern: a mix of rounded and ellipsoidal sculpture. Mesh width: 1.5-12.0 µm. Teleoconch. Colour: orange. First whorl: convex. Subsequent whorls: convex. Suture: well-impressed. Shoulder: narrow. Number of whorls: 2 ¾– 3 ¼. SH: 1.78-2.11 mm. SW: 1.21-1.40 mm. SI: 1.42-1.51. Shell sculpture. Radial sculpture: absent, weak growth lines present throughout the shell surface. Spiral sculpture: present, strong, regularly spaced, ca. 10-12 spiral ribs on the body whorl of the adult individual, developed immediately after the protoconch; more densely spaced spiral ribs at the basal part of the body whorl, becoming weaker closer to the columellar region. Aperture. Shape: rounded to slightly ovoid, straight to concave parietal side, palatal edge contiguous with the body whorl, basal side convex. AH: 0.66-0.79 mm. AW: 0.74-0.84 mm. AI: 0.89-0.94. Holotype dimensions. SH: 2.11 mm, SW: 1.40 mm, AH: 0.79 mm, AW: 0.84 mm.

Diagnosis.

Georissa insulae is characterised by the strong and regularly spaced spiral ribs throughout the entire shell. This shell sculpture is similar to that of G. hungerfordi and G. trusmadi , but less raised than in these two species. Georissa insulae has a greater number of spiral ribs, ca. 10-12 ribs on its shell compared to these two species. The shell habitus is distinctly elongated compared to other spirally ribbed Bornean Georissa .

Distribution.

Known from islands of Mantanani Kecil, Mantanani Besar, Lungisan, and on the mainland from Pitas to Kinabalu National Park, Sabah.

Molecular analysis.

ML and Bayesian analyses of G. insulae (16S: n = 4) show that G. filiasaulae form one clade with 100% BS and 100% PP. Sister to the rest of “non-scaly” Georissa , except for G. hungerfordi + G. gomantonensis + G. filiasaulae .