Georissa hosei Godwin-Austen, 1889

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 hosei Godwin-Austen, 1889

Georissa hosei Godwin-Austen, 1889: 353, fig. 11 plate XXXIX; Smith 1893: 351, fig. 27 plate XXV; Thompson and Dance 1983: 116.

Type locality.

Borneo. (Unspecified)

Type material.

Lectotype (Designated by Thompson and Dance 1983). Borneo: NHMUK 1889.12.7.72 (glued on paper) (seen).

Other material.

Jambusan, North Borneo: NHMUK 92.7.20.122, NHMUK 92.7.23.33-4. Gunung Liak/Padang, Kampung Skiat Baru, Jambusan, Sarawak (01°24.05'N, 110°11.19'E): MZU/MOL 16.04, MZU/MOL 16.05, MZU/MOL 16.06, MZU/MOL 16.07. Bukit Siboyuh, Kampung Skiat Baru, Jambusan, Sarawak (01°22.90'N, 110°11.69'E): MZU/MOL 16.08. Bukit Tongak, Bidi, Bau/Jambusan, Sarawak (01°22.67'N, 110°08.32'E): MZU/MOL 16.09.

Description.

Protoconch. Color: red. Sculpture pattern: smooth. Teleoconch. Color: orange to red. First whorl: rounded or shouldered with flat surfaces above and below the shoulder. Subsequent whorls: convex to rounded; number of whorls: 2-2 ¼. SH: 1.06-1.55 mm, SW: 1.09-1.60 mm, SI: 0.94-1.12. Shell sculpture. Radial sculpture: absent, only weak growth lines. Spiral sculpture: present, weakly sculpted, continuous ribs, more prominent at the periphery. Scales: two to four series of low and broad vertical scales, regularly spaced, the upper scale series always the strongest, weaker series appear later at the spire, and the spaces between series are irregular. Aperture. Shape: oval. Basal side: rounded, angular at the columellar region. Parietal side: straight, palatal edge attached or removed at the body whorl. AH: 0.60-0.95 mm, AW: 0.80-1.16 mm, AI: 0.74-0.88.

Cross diagnosis.

Georissa hosei has a diagnostic smooth protoconch. It possesses similar shell habitus and scale characters as G. sepulutensis , G. pyrrhoderma , and G. kobelti . However, the scales of G. hosei are rarely developed into large and acutely projected scales.

Distribution.

Known from Gunung Liak/Padang and Bukit Siboyuh at Kampung Skiat Baru, Jambusan, and Bukit Tongak, in the area of Bau, which is close to Jambusan.

Molecular analysis.

ML and Bayesian analyses shows that all G. hosei individuals (16S: n = 21; CO1: n = 11) group together in one clade with 100% BS and 100% PP, which is the sister group of all other "scaly group" species, except G. saulae .

Discussion.

Godwin-Austen (1889), when he described the species, mentioned that the sides of the spire (whorls) are flat, which we find to be the case for the first whorl in our material (as well as in the lectotype). The exact type locality was not specified, but Smith (1893) reported that the specimens of G. hosei described by Godwin-Austen (1889) were from Jambusan, Sarawak. It has to be noted that G. hosei is highly variable in shell shape and sculpture, even within a local population. For example, material we collected at Gunung Liak/Padang have anything between two and four series of broad and low scales. Material from Bukit Tongak has three to four spiral threads with scales. Material from Bukit Siboyuh, finally, is brighter in color (orange), with only one or two spiral series of scales. These three limestone outcrops are all within the area of not more than 10 km radius. Thompson and Dance (1983) noted that G. hosei is widely distributed in Sarawak, and they give Baram, Marudi, Niah, Tatau, and Bukit Sarang as localities. However, as we elaborate in this paper, many of these populations are not conspecific with G. hosei . For example, the image of " G. hosei " provided by Thompson and Dance (1983) - UF 35919, from Batu Gading, Baram, appears conspecific to G. kobelti . Also, their " G. hosei " from Bukit Sarang we here describe as a G. anyiensis sp. n.