Georissa anyiensis , 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

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Georissa anyiensis

sp. n.

Georissa anyiensis  sp. n.

Georissa hosei  Godwin-Austen: Thompson and Dance 1983: 117, materials from Tatau Valley, Bukit Sarang, Bintulu, Sarawak. (non G. hosei  Goodwin-Austen, 1889)

Type locality.

Bukit Anyi at Bukit Sarang, Bintulu, Sarawak, Malaysia (02°39.25'N, 113°02.72'E).

Type material.

Holotype. Bukit Anyi at Bukit Sarang, Bintulu, Sarawak, Malaysia (02°39.25'N, 113°02.72'E): MZU/MOL 17.90 (leg. MZ Khalik and SK Reduan). Paratypes. Bukit Anyi at Bukit Sarang, Bintulu, Sarawak (02°39.25'N, 113°02.72'E): MZU/MOL 17.53, MZU/MOL 17.54, MZU/MOL 17.55, MZU/MOL 17.56, MZU/MOL 17.57, MZU/MOL 17.58, MZU/MOL 17.59, MZU/MOL 17.60, MZU/MOL 17.61, JJV 12840 (40), JJV 12841 (1). Bukit Lebik at Bukit Sarang, Bintulu, Sarawak (02°39.32'N, 113°02.43'E): MZU/MOL 17.50, MZU/MOL 17.51, MZU/MOL 17.52, JJV 12842 (20), JJV 12843 (1). From Thompson and Dance 1983, Bukit Sarang, Tatau valley (20°45'N, 113°02'E): UF 35914, UF 35915, UF 35921 (not seen). Each lot of examined paratypes from MZU are more than 50 individuals.


Named after the hill Bukit Anyi at Bukit Sarang, Bintulu, Sarawak, Malaysia, the type locality.


Protoconch. Color: yellow to orange. Sculpture pattern: meshed - rounded to ellipsoidal or undefined mesh shape. Mesh width: 8-30 µm. Teleoconch. Color: yellow. First whorl: shouldered, cylindrical. Subsequent whorls: convex to rounded, with a deeply impressed suture. SH: 1.39-1.98 mm, SW: 1.32-1.72 mm, SI: 1.05-1.08. Total number of whorls: 2 ¼– 2 ¾. Shell sculpture. Radial sculpture: absent, only weak to strong growth lines are visible. Spiral sculpture: present, strongly sculpted, continuous ribs, more prominent at the periphery. Scales: at the shoulder a continuous spiral row of highly projecting diagonal crown-like scales; subordinate to that, three to four series of tall, broad or acute diagonal scales, regularly spaced, the uppermost of these always stronger than the lower ones, inter-series pacing irregular. Aperture. Shape: oval to rounded. Basal side: rounded, angular at the columellar region. Parietal side: straight. AH: 0.67-0.91 mm, AW: 0.90-1.17 mm, AI: 0.74-0.93. Holotype dimension. SH: 1.91 mm, SW: 1.72 mm, AH: 0.90 mm, AW: 1.14 mm.

Cross diagnosis.

In general, G. anyiensis  has a shell shape that is similar to G. kobelti  , G. scalinella  , and G. muluensis  . However, G. anyiensis  has an extremely prominent, crown-like spiral series of large scales on the shell periphery, which distinguishes it from other “scaly” Georissa  .


Known from Bukit Anyi and Bukit Lebik, two isolated hills at Bukit Sarang, Bintulu, Sarawak.

Molecular analysis.

ML and Bayesian analyses show that the G. anyiensis  individuals (16S: n = 13; CO1: n = 12) form a monophyletic group with 100% BS and 100% PP, sister group to the four species G. niahensis  + G. kobelti  + G. hadra  + G. muluensis  .