Georissa kinabatanganensis, 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 kinabatanganensis sp. n.

Type locality.

Bukit Keruak, near Kinabatangan river, Sandakan, Sabah, Malaysia (05°31.385'N, 118°17.113'E).

Type material.

Holotype. Bukit Keruak, near Kinabatangan river, Sandakan, Sabah, Malaysia (05°31.38'N, 118°17.11'E): BOR/MOL 13921 (leg. M Schilthuizen). Paratypes. Bukit Keruak, near Kinabatangan river, Sandakan, Sabah (05°31.38'N, 118°17.11'E): MZU/MOL 17.26 (>50). BOR/MOL 1458, BOR/MOL 11656, BOR/MOL 11665, BOR/MOL 11711, BOR/MOL 13871. Batu Pangi, Sabah: BOR/MOL 1455. Batu Tomanggong, Sabah: BOR/MOL 1456, BOR/MOL 1457, BOR/MOL 10530.

Etymology.

Named after the district of Kinabatangan, Sabah, Malaysia, where the type locality Bukit Keruak is located.

Description.

Protoconch. Color: orange. Sculpture pattern: smooth to meshed - rounded to undefined mesh pattern. Mesh width: 14-21 µm. Teleoconch. Color: orange. First whorl: flat and angular at the shoulder. Subsequent whorls: angular, slightly rounded at the periphery, with number of whorls: 2-2 ¼. SH: 1.00-1.32 mm, SW: 1.13-1.37 mm, SI: 0.85-0.99. Shell sculpture. Radial sculpture: absent, only weak to strong growth lines are visible. Spiral sculpture: present, and strongly sculpted, with continuous to discontinuous ribbings. Scales: two series of diagonal vertical scales, widely spaced in between, both series are strongly sculpted, broad, and the scales are regularly placed. Aperture. Shape: oval. Basal side: rounded, angular at the columellar region. Parietal side: straight, palatal edge attached to the body whorl. AH: 0.54-0.66 mm, AW: 0.75-0.86 mm, AI: 0.65-0.80. Holotype dimension. SH: 1.00 mm, SW: 1.18 mm, AH: 0.54 mm, AW: 0.78 mm.

Cross diagnosis.

Georissa kinabatanganensis has less variation in shell sculpture compared with G. hosei and G. scalinella . G. kinabatanganensis has two series of acutely projected scales on the whorls. In some cases, the second scale series is weaker than the first, and creates a series of nodular structures at the periphery. Often the shell is wider than high, which gives it a flattened appearance. In addition, G. kinabatanganensis has widely spaced between the scale series, similar to G. muluensis .

Distribution.

Known from Bukit Keruak, Batu Tomanggong, and Pangi, in the region of Kinabatangan, Sabah.

Molecular analysis.

RAxML and Bayesian analyses show G. kinabatanganensis (16S: n = 6; CO1: n = 6) forming a clade with 97% BS and 97% PP and as a sister clade to G. sepulutensis .

Discussion.

Georissa kinabatanganensis is the only species in "scaly group" Georissa to have a flat shell habitus, all examined individuals have a shell that is broader than high.