Georissa bauensis, Khalik, Mohd Zacaery, Hendriks, Kasper, Vermeulen, Jaap J. & Schilthuizen, Menno, 2018

Khalik, Mohd Zacaery, Hendriks, Kasper, Vermeulen, Jaap J. & Schilthuizen, Menno, 2018, A molecular and conchological dissection of the " scaly " Georissa of Malaysian Borneo (Gastropoda, Neritimorpha, Hydrocenidae), ZooKeys 773, pp. 1-55 : 1

Georissa bauensis sp. n.

Type locality.

Wind Cave Passage 3, Wind Cave Nature Reserve, Bau, Sarawak, Malaysia (01°24.81'N, 110°08.17'E).

Type material.

Holotype. Wind Cave Passage 3, Wind Cave Nature Reserve, Bau, Sarawak, Malaysia (01°24.81'N, 110°08.17'E): MZU/MOL 17.89 (leg. MZ Khalik). Paratypes. Wind Cave Passage 3, Wind Cave Nature Reserve, Bau, Sarawak, Malaysia (01°24.81'N, 110°08.17'E): MZU/MOL 16.01 (25), MZU/MOL 16.02 (>50). Gunung Podam, near Sungai Ayup, Kampung Bogag, Bau, Sarawak, Malaysia (01°21.15'N, 110°03.57'E): MZU/MOL 16.03 (5).

Etymology.

Named after the district of Bau, Sarawak, Malaysia, where the type locality Wind Cave Nature Reserve is located.

Description.

Protoconch. Color: red. Sculpture pattern: meshed - rounded or irregular mesh shape. Mesh width: 12-22 µm. Teleoconch. Color: orange to red. First whorl: shouldered, flat both above and below the shoulder. Subsequent whorls: convex shoulder and more rounded at the periphery. SH: 1.16-1.62 mm, SW: 1.06-1.30 mm, SI: 1.02-1.25. Total number of whorls: 2-2 ½. Shell sculpture. Radial sculpture: absent, only weak growth lines are visible. Spiral sculpture: present, weakly to strongly sculpted, continuous to discontinuous ribs, more prominent at the periphery. Scales: two to three major spiral series of low and small diagonal scales, regularly spaced, the upper series always stronger than the lower ones, scale series irregularly spaced. Aperture. Shape: rounded and tilted below. Basal side: rounded, angular at the columellar region. Parietal side: straight. AH: 0.57-0.78 mm, AW: 0.69-0.86 mm, AI: 0.74-0.96. Holotype dimension. SH: 1.16 mm, SW: 1.06 mm, AH: 0.58 mm, AW: 0.70 mm.

Cross diagnosis.

Georissa bauensis is very similar to G. kobelti (although not closely related phylogenetically), in terms of general shell shape and spiral scale characters. However, G. bauensis is sufficiently variable to include specimens that are more similar to G. hosei and G. scalinella . Furthermore, G. bauensis has more strongly sculpted scales than G. hosei , and a more rounded and convex shell than G. scalinella .

Distribution.

Known from Gunung Podam and Wind Cave Nature Reserve, Bau, Sarawak.

Molecular analysis.

ML and Bayesian analyses resolve all individuals of G. bauensis (16S: n = 13; CO1: n = 8) as a monophyletic group with 99% BS and 100% PP, the sister group of G. silaburensis .