Georissa kobelti Gredler, 1902

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

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Georissa kobelti Gredler, 1902


Georissa kobelti Gredler, 1902 

Georissa kobelti  Gredler, 1902: 61; Zilch 1973: 265, fig. 11; Thompson and Dance 1983: 117, fig. 28, 50-52.

Georissa hosei  Godwin-Austen: Thompson and Dance 1983: 117, fig. 47-49, material from Bukit Besungai at Baram Valley, Niah, Kejin trib. of Baram river (non G. hosei  Goodwin-Austen, 1889).

Type locality.

Niah, Baram (Sarawak, Borneo). Unspecified.

Type material.

Lectotype (Designated by Zilch 1973). Niah, Baram (Sarawak, Borneo): SMF 215893a (not seen).

Other material.

Trade Cave, Niah National Park, Niah, Sarawak (03°49.13'N, 113°46.86'E): MZU/MOL 17.36. Great Cave, Niah National Park, Niah, Sarawak: MZU/MOL 17.37. Bukit Kaijin, Baram, Sarawak (03°41.75'N, 114°27.55'E): MZU/MOL 17.38, MZU/MOL 17.39, MZU/MOL 17.40, MZU/MOL 17.41, MZU/MOL 17.42, MZU/MOL 17.43, MZU/MOL 17.44, MZU/MOL 17.45, MZU/MOL 17.46, MZU/MOL 17.47, MZU/MOL 17.48, MZU/MOL 17.49, JJV 10217. Bukit Kasut, Niah N.P., Niah, Sarawak: JJV 10254. Niah N.P., Niah, Sarawak: JJV 1565, JJV 5466, JJV 10306, JJV 10392. Deer Cave, Mulu N.P., Mulu, Sarawak: JJV 10533 (the sample, approximately 150 individuals, also contains G. muluensis  and G. hadra  ). Tatau river valley, Bukit Sarang, Bintulu, Sarawak: JJV 12551, JJV 12838. From Thompson and Dance 1983, Niah, Baram (Sarawak, Borneo): UF 35919, UF 36179 (not seen).


Protoconch. Color: orange to red. Sculpture: meshed - semi-oval mesh shape. Mesh width: 11-22 µm. Teleoconch. Color: ranging from red to yellow. First whorl: convex to rounded. Subsequent whorls: convex to rounded. SH: 1.75-2.11 mm, SW: 1.48-1.75 mm, SI: 1.18-1.28. Total number of whorls: 2 ¾ -3. Shell sculpture. Radial sculpture: absent, only weak growth lines. Spiral sculpture: present with thin but strongly continuous spiral ribs, forming small acute scales near the suture. Scales: three to four spiral rows of tilted, nearly vertical scales, the upper series stronger than the lower ones, scale prominence ranging from high to low and from small and acute to broadly sculpted and ear-like. Scales are regularly spaced, as are the scale series themselves. Aperture. Shape: rounded to oval. Basal side: rounded, angular before the columellar region. Parietal side: curved. AH: 0.82-1.04 mm, AW: 1.02-1.17 mm, AI: 0.71-0.90.

Cross diagnosis.

The image of the G. kobelti  lectotype by Zilch (1973) does not provide detailed information about the scale characters of G. kobelti  as compared to the images of the individual from UF provided by Thompson and Dance (1983), which clearly shows the diagnostic characters of the ear-like scale pattern of this species. In shell habitus, G. kobelti  is similar to some populations of G. anyiensis  , G. saulae  , and G. hosei  , but these species differ from G. kobelti  by the pattern of their diagonal scales.


The lectotype in Senckenberg (SMF 215893a) was obtained from an unspecified location. As far as known, the species is restricted to the area of Niah to Baram, northern Sarawak. Thompson and Dance (1983) also stated that they examined this species from Beluru, which is located between Niah and Baram.

Molecular analysis.

In the ML and Bayesian analyses of G. kobelti  (16S: n = 8; CO1: n = 8), the Niah and Baram populations form highly supported clades (99% and 100% BS, respectively, and 100% PP for both clades), which are paraphyletic with respect to G. niahensis  .