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A molecular and conchological dissection of the “scaly” Georissa of Malaysian Borneo (Gastropoda, Neritimorpha, Hydrocenidae)
expand article infoMohd Zacaery Khalik§|, Kasper Hendriks, Jaap J. Vermeulen#, Menno Schilthuizen§¤
‡ Naturalis Biodiversity Center, Leiden, Netherlands
§ Leiden University, Leiden, Netherlands
| Universiti Malaysia Sarawak, Sarawak, Malaysia
¶ University of Groningen, Groningen, Netherlands
# JK Art and Science, Leiden, Netherlands
¤ Universiti Malaysia Sabah, Sabah, Malaysia
Open Access

Abstract

The Bornean hydrocenids have so far been understudied compared to other non-pulmonate snails in this region. In the present study, we review a first group of minute land snail species belonging to the genus Georissa (Gastropoda, Hydrocenidae) from Malaysian Borneo. This group is restricted to the species with conspicuous scale-like sculpture on the shell. Based on materials from recent fieldwork, museums, and personal collections, Malaysian Borneo hydrocenids are more complex and diverse in shell characters than previously anticipated. Here, a molecular, conchological, and biogeographic study of this “scaly group” is presented. We recognise 13 species of which six are new to science, namely Georissa anyiensis sp. n., Georissa muluensis sp. n., Georissa bauensis sp. n., Georissa silaburensis sp. n., Georissa kinabatanganensis sp. n., and Georissa sepulutensis sp. n.

Keywords

Gastropods, land snail, limestone karst, Malaysian Borneo, micro-computed tomography, Sabah, Sarawak, species delimitation

Introduction

Over the past 25 years, the microsnail fauna of karst habitats in South East Asia has enjoyed an ongoing surge of attention. Detailed conchological and molecular studies in this region have revealed high allopatric and sympatric diversity (e.g., Liew et al. 2014, Rundell 2008, Tongkerd et al. 2004), which has opened up this fauna for work in the fields of community ecology (Schilthuizen et al. 2005, Schilthuizen 2011), speciation (Schilthuizen et al. 2006, Schilthuizen et al. 2012), and conservation biology (Clements et al. 2006, Clements et al. 2008, Schilthuizen et al. 2005). Although several families of non-pulmonate snails have featured prominently in these studies (in particular the Diplommatinidae and other cyclophoroids), the family Hydrocenidae (Neritimorpha) has so far been understudied. In this paper, we make a start with a first conchological and molecular characterisation of a surprisingly diverse group of species in the genus Georissa Blanford, 1864.

The genus Georissa Blanford, 1864 is characterised by a calcareous, rounded to ovate concentric, paucispiral operculum, with a calcareous peg emerging from the inner surface (Bandel 2008, Thompson and Dance 1983, Vermeulen et al. 2015). The shell is small, dextral, conical, and frequently presents conspicuous radial and spiral sculpture. The studies by Thompson and Dance (1983) and Vermeulen et al. (2015) showed that the Bornean Georissa are between 0.7 and 4.0 mm in adult shell height. The protoconch is usually distinctly hemi-spherically shaped, distinct in microsculpture and distinguishable from the post-embryonic whorls. The internal walls (some would refer these as septa) are resorbed, and the remaining wall ends more than one whorl before reaching the aperture; resorption also leads to excavation of the columella (Thompson and Dance 1983, Bandel 2008). The evolutionary causes for this internal shell restructuring remain to be studied. The snails are often found in moderate to high densities on rocks, especially limestone rocks, where they apparently forage moss, algae, and lichens (Berry 1966). Cave-adapted species may forage on bacterial films (Schilthuizen et al. 2012).

Previous taxonomic treatments of Bornean Georissa (Godwin-Austen 1889, Gredler 1902, Haase and Schilthuizen 2007, Smith 1893, 1895, Thompson and Dance 1983, van Benthem-Jutting 1966, Vermeulen and Junau 2007, Vermeulen et al. 2015) revealed that shell shape and size, as well as sculptural patterns on the whorls are important characters for species delimitation. Given the small size of these shells, great benefits can be had from the use of scanning electron microscopy and X-ray microtomography, which are able to show detailed microscopic sculpture patterns and the inner part of the shell.

Since the overview presented by Thompson and Dance (1983), no revisions have been made for the Bornean Georissa, although recently, several new Bornean Georissa have been described, i.e., Georissa filiasaulae Haase & Schilthuizen, 2007, Georissa pachysoma Vermeulen & Junau, 2007, Georissa leucococca Vermeulen et al., 2015 and Georissa nephrostoma Vermeulen et al., 2015. Our new studies of the Georissa of Malaysian Borneo reveal additional, previously unrecognized diversity, which warrants a series of revisions of the various species groups. In the present paper, we first address a group of species that we here call the “scaly group”, chiefly consisting of species with conspicuous scale-like sculpture on the shell.

We present detailed species descriptions for a total of 13 Bornean Georissa from the “scaly group”, of which six species are new to science, namely: Georissa anyiensis sp. n., Georissa muluensis sp. n., Georissa bauensis sp. n., Georissa silaburensis sp. n., Georissa kinabatanganensis sp. n., and Georissa sepulutensis sp. n.

Materials and methods

Materials and fieldwork

We examined collection material from:

RMNH Naturalis Biodiversity Center (previously collection from Rijksmuseum van Natuurlijke Historie), Leiden,

ZMA Naturalis Biodiversity Center (previously collection from Zoological Museum of Amsterdam), Leiden,

NHMUK Natural History Museum, London,

BORN Universiti Malaysia Sabah,

MZU Zoology Museum, Universiti Malaysia Sarawak, and

JJV Jaap Vermeulen (personal collection).

In addition to these available data, we did fieldwork at limestone outcrops in Malaysian Borneo between September 2015 and May 2017. Manual searches were carried out to collect living and empty shells of Georissa on limestone walls and rocks, loose organic matter, and on/under living leaves. The living Georissa were directly stored in sample tubes containing ~96% ethanol. Ca. 5 litres of soil and leaf litter were sampled at each sampling location to collect empty shells by flotation (Vermeulen and Whitten 1998). The holotypes, paratypes and all of the collected materials were deposited at the Zoology Museum (Universiti Malaysia Sarawak, Kota Samarahan, Sarawak, Malaysia), Borneensis Collection (Universiti Malaysia Sabah, Kota Kinabalu, Sabah, Malaysia), and Naturalis Biodiversity Centre (Leiden, The Netherlands).

Morphological analysis

Microscopy. Shells were observed with a Zeiss SteREO Microscope Discovery V20. The images of examined individuals were captured by AxioCamMRc5, Zeiss PlanApo S 1.0× FWD 60.0mm lenses. A complementary software of the camera AxioVision Special Edition 64-bit version 4.9.1.0 was used for shell measurements, namely, shell height, shell width, aperture height, and aperture width, at 30–60× magnification. The measurements of “scaly” Georissa were carried out following the shell measurement method of Vermeulen and Whitten 1998. Scanning electron microscopy. A representative adult shell for each species was cleaned using sodium hypochloride, dried, and sputter-coated with Pd/Pt coating agent before detailed examination with a JEOL JSM-6480LV scanning electron microscope (SEM). We obtained SEM images of the entire shell in top view and apertural view (including clear view of the sculpture), side and top views of the protoconch and the spire. Micro-computed tomography. The micro-computed tomography (µCT) scanning was carried out with an Xradia 520 Versa X-ray Microscope using accompanying software Zeiss Xradia Versa (11.1.6315). The X-ray images from the scanning (ca. 950 layers of images in TIF format) were reconstructed into composite 3D images of the shells using software Scout-and-ScanTM Control System Reconstructor (11.1.5707.17179). All shell materials were scanned in air medium at 80/7 voltage/power (kW/P) using objective lens unit 4 in 180° rotation. Detailed scanning parameters for each species are summarized in Suppl. material 1. We used reconstructed 3D images of representative adult shells of each species from µCT scanned data to examine the internal characters, including the operculum and its peg. We conducted 3D image reconstruction to preserve the original structure of the shells and avoiding unintentional shell destruction. The 3D image analysis of the shells was carried out with Avizo ver. 9.2.0, FEI Company.

Molecular analysis

DNA extraction. Genomic DNA was extracted from 127 individuals of Georissa using the Qiagen DNeasy Blood and Tissue kit, following the manufacturer’s protocol. Prior to the DNA extraction, the shells were removed and the entire soft tissue was used in the DNA extraction procedure. DNA amplification. We amplified two mtDNA regions, namely 16S and CO1. DNA amplifications were conducted on a BIO-RAD C1000 Touch Thermal Cycler. For the 16S gene, a fragment of 422-464 bp was amplified using primer pair LR-J-12887 5’-CCGGTCTGAACTCAGATCACGT-3’ (forward) and LR-N-13398 5’-CGCCTGTTTAACAAAAAACAT-3’ (reverse) (Schilthuizen et al. 2005) in 25.0 µL reaction volume, containing: 1.0 µL undiluted DNA template, 15.0 µL mQ (milli-Q, ultrapure water), 2.5 µL PCR chlorine buffer 10×, 2.5 µL MgCl2 25.0 mM, 0.25 µL BSA 100 mM, 1.0 µL forward primer 10 pmol/µL, 1.0 µL reverse primer 10 pmol/µL, 1.5 µL dNTPs 2.5 mM, and 0.25 µL Taq 5.0 U/ µL. The amplification was carried out with the following cycling protocol: initial denaturation at 95 °C for 5 min, 36 cycles (of denaturation at 95 °C for 30 s, annealing at 52 °C for 30 s, extension at 72 °C for 1 min), and a final extension at 72 °C for 5 min. A 546-603 bp fragment of CO1 was amplified using primer pair LCO1490 5’-GGTCAACAAATCATAAAGATATTGG-3’ (forward) and HCO2198 5’-TAAACTTCAGGGTGACCAAAAAATCA-3’ (reverse) (Folmer et al. 1994) in 25.0 µL reaction volume, containing: 1.0 µL DNA template, 16.8 µL mQ, 2.5 µL PCR chlorine buffer 10×, 1.0 µL MgCl2 25.0 mM, 1.0 µL BSA 100 mM, 1.0 µL forward primer 10 pmol/µL, 1.0 µL reverse primer 10 pmol/µL, 0.5 µL dNTPs 2.5 mM, and 0.25 µL Taq 5.0 U/µL. The amplification was carried out with the following cycling protocol: initial denaturation at 94 °C for 4 min, 40 cycles (of denaturation at 94 °C for 15 s, annealing at 50 °C for 30 s, extension at 72 °C for 40 s), and a final extension at 72 °C for 5 min. The unsuccessful amplication of CO1 and 16S genes were excluded in further phylogenetic analysis that used concatenated sequence alignment of both genes. Sequencing. The PCR products were then Sanger sequenced in both directions at BaseClear B.V. (Leiden, The Netherlands) on the ABI3730XL sequencer from Life Technologies. All new 16S mtDNA sequences used in this study were deposited in GenBank (https://www.ncbi.nlm.nih.gov/genbank/) and CO1 mtDNA sequences were deposited in GenBank via BOLD (http://boldsystems.org/), under accession numbers as listed in Table 1.

List of specimens used in molecular analyses.

No. Species Voucher No. Species name_sequence origin_locationTown/District/Division, State. GPS coordinate GenBank Accession No.
16S CO1
1 Georissa gomantongensis Smith, 1893 BOR/MOL 7389 G.gomantongensis_KPH01833.01_KinabatanganKinabatangan Valley, Sabah. 05°30.913'N, 118°16.889'E MG982259 MH033876
2 Georissa gomantongensis Smith, 1893 BOR/MOL 7389 G.gomantongensis_KPH01833.02_KinabatanganKinabatangan Valley, Sabah. 05°30.913'N, 118°16.889'E MG982260 MH033875
3 Georissa saulae (van Benthem Jutting, 1966) BOR/MOL 2663-2667 (Schilthuizen et al. 2012) G.saulae_AY547385_SinobangBatu Sinobang, Sabah. 04°48.040'N, 116°37.035'E AY547385 n.a.
4 Georissa saulae (van Benthem Jutting, 1966) BOR/MOL 2663-2667 (Schilthuizen et al. 2012) G.saulae_hapA_AY547380_SanaronSepulut Valley, Batu Sanaron, Sabah. 04°42.052'N, 116°36.016'E AY547380 n.a.
5 Georissa saulae (van Benthem Jutting, 1966) BOR/MOL 2663-2667 (Schilthuizen et al. 2012) G.saulae_hapB_AY547381_SanaronSepulut Valley, Batu Sanaron, Sabah. 04°42.052'N, 116°36.016'E AY547381 n.a.
6 Georissa saulae (van Benthem Jutting, 1966) BOR/MOL 2663-2667 (Schilthuizen et al. 2012) G.saulae_hapC_AY547384_SanaronSepulut Valley, Batu Sanaron, Sabah. 04°42.052'N, 116°36.016'E AY547384 n.a.
7 Georissa saulae (van Benthem Jutting, 1966) BOR/MOL 3493 G.saulae_ZI003_SanaronSepulut Valley, Batu Sanaron, Sabah. 04°42.052'N, 116°36.016'E MG982261 n.a.
8 Georissa saulae (van Benthem Jutting, 1966) BOR/MOL 3493 G.saulae_KPH00181.02_SanaronSepulut Valley, Batu Sanaron, Sabah. 04°42.052'N, 116°36.016'E MG982267 n.a.
9 Georissa saulae (van Benthem Jutting, 1966) BOR/MOL 12770 G.saulae_Sau-001_PungitonSepulut Valley, Gua Pungiton, Sabah. 04°42.410'N, 116°36.040'E MG982262 n.a.
10 Georissa saulae (van Benthem Jutting, 1966) BOR/MOL 12770 G.saulae_Sau-002_PungitonSepulut Valley, Gua Pungiton, Sabah. 04°42.410'N, 116°36.040'E MG982263 n.a.
11 Georissa saulae (van Benthem Jutting, 1966) BOR/MOL 12770 G.saulae_Sau-003_PungitonSepulut Valley, Gua Pungiton, Sabah. 04°42.410'N, 116°36.040'E MG982264 n.a.
12 Georissa saulae (van Benthem Jutting, 1966) BOR/MOL 12770 G.saulae_Sau-004_PungitonSepulut Valley, Gua Pungiton, Sabah. 04°42.410'N, 116°36.040'E MG982265 n.a.
13 Georissa saulae (van Benthem Jutting, 1966) BOR/MOL 12770 G.saulae_Sau-005_PungitonSepulut Valley, Gua Pungiton, Sabah. 04°42.410'N, 116°36.040'E MG982266 n.a.
14 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.09 G.hosei_A001_TongakBukit Tongak, Bidi, Bau/Jambusan, Sarawak. 01°22.670'N, 110°08.325'E MG982327 n.a.
15 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.09 G.hosei_A002_TongakBukit Tongak, Bidi, Bau/Jambusan, Sarawak. 01°22.670'N, 110°08.325'E MG982331 MH033908
16 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.09 G.hosei_A003_TongakBukit Tongak, Bidi, Bau/Jambusan, Sarawak. 01°22.670'N, 110°08.325'E MG982330 n.a.
17 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.09 G.hosei_A004_TongakBukit Tongak, Bidi, Bau/Jambusan, Sarawak. 01°22.670'N, 110°08.325'E MG982329 MH033907
18 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.09 G.hosei_A005_TongakBukit Tongak, Bidi, Bau/Jambusan, Sarawak. 01°22.670'N, 110°08.325'E MG982328 n.a.
19 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.09 G.hosei_A006_TongakBukit Tongak, Bidi, Bau/Jambusan, Sarawak. 01°22.670'N, 110°08.325'E MG982326 n.a.
20 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.04 G.hosei_C001_LiakGunung Liak/Padang, Kampung Skiat Baru, Jambusan, Sarawak. 01°24.050'N, 110°11.197'E MG982339 MH033904
21 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.04 G.hosei_C002_LiakGunung Liak/Padang, Kampung Skiat Baru, Jambusan, Sarawak. 01°24.050'N, 110°11.197'E MG982338 MH033905
22 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.04 G.hosei_C003_LiakGunung Liak/Padang, Kampung Skiat Baru, Jambusan, Sarawak. 01°24.050'N, 110°11.197'E MG982341 MH033902
23 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.04 G.hosei_C004_LiakGunung Liak/Padang, Kampung Skiat Baru, Jambusan, Sarawak. 01°24.050'N, 110°11.197'E MG982340 MH033903
24 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.04 G.hosei_C005_Liak Gunung Liak/Padang, Kampung Skiat Baru, Jambusan, Sarawak. 01°24.050'N, 110°11.197'E MG982337 n.a.
25 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.04 G.hosei_C006_LiakGunung Liak/Padang, Kampung Skiat Baru, Jambusan, Sarawak. 01°24.050'N, 110°11.197'E MG982336 MH033906
26 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.04 G.hosei_C007_Liak Gunung Liak/Padang, Kampung Skiat Baru, Jambusan, Sarawak. 01°24.050'N, 110°11.197'E MG982335 n.a.
27 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.04 G.hosei_C008_Liak Gunung Liak/Padang, Kampung Skiat Baru, Jambusan, Sarawak. 01°24.050'N, 110°11.197'E MG982334 n.a.
28 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.04 G.hosei_C009_LiakGunung Liak/Padang, Kampung Skiat Baru, Jambusan, Sarawak. 01°24.050'N, 110°11.197'E MG982333 n.a.
29 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.04 G.hosei_C0010_LiakGunung Liak/Padang, Kampung Skiat Baru, Jambusan, Sarawak. 01°24.050"N, 110°11.197"E MG982332 n.a.
30 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.08 G.hosei_D001_SiboyuhBukit Siboyuh, Kampung Skiat Baru, Jambusan, Sarawak.01°22.909'N, 110°11.695'E MG982346 MH033900
31 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.08 G.hosei_D002_SiboyuhBukit Siboyuh, Kampung Skiat Baru, Jambusan, Sarawak.01°22.909'N, 110°11.695'E MG982342 MH033901
32 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.08 G.hosei_D003_SiboyuhBukit Siboyuh, Kampung Skiat Baru, Jambusan, Sarawak.01°22.909'N, 110°11.695'E MG982345 MH033898
33 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.08 G.hosei_D004_SiboyuhBukit Siboyuh, Kampung Skiat Baru, Jambusan, Sarawak.01°22.909'N, 110°11.695'E MG982344 MH033899
34 Georissa hosei Godwin-Austen, 1889 MZU/MOL 16.08 G.hosei_D006_SiboyuhBukit Siboyuh, Kampung Skiat Baru, Jambusan, Sarawak.01°22.909'N, 110°11.695'E MG982343 n.a.
35 Georissa anyiensis sp. n. MZU/MOL 17.50 G.anyiensis_BSP2-01_Bukit SarangPlot 2, Bukit Lebik at Bukit Sarang, Bintulu, Sarawak.02°39.325'N, 113°02.432'E MG982271 MH033929
36 Georissa anyiensis sp. n. MZU/MOL 17.50 G.anyiensis_BSP2-02_Bukit SarangPlot 2, Bukit Lebik at Bukit Sarang, Bintulu, Sarawak.02°39.325'N, 113°02.432'E MG982269 MH033930
37 Georissa anyiensis sp. n. MZU/MOL 17.50 G.anyiensis_BSP2-03_Bukit SarangPlot 2, Bukit Lebik at Bukit Sarang, Bintulu, Sarawak.02°39.325'N, 113°02.432'E MG982268 MH033928
38 Georissa anyiensis sp. n. MZU/MOL 17.50 G.anyiensis_BSP2-04_Bukit SarangPlot 2, Bukit Lebik at Bukit Sarang, Bintulu, Sarawak.02°39.325'N, 113°02.432'E MG982270 n.a.
39 Georissa anyiensis sp. n. MZU/MOL 17.51 G.anyiensis_BSP11-01_Bukit SarangPlot 11, Bukit Lebik at Bukit Sarang, Bintulu, Sarawak.02°39.325'N, 113°02.432'E n.a. MH033926
40 Georissa anyiensis sp. n. MZU/MOL 17.51 G.anyiensis_BSP11-02_Bukit SarangPlot 11, Bukit Lebik at Bukit Sarang, Bintulu, Sarawak.02°39.325'N, 113°02.432'E MG982278 MH033927
41 Georissa anyiensis sp. n. MZU/MOL 17.51 G.anyiensis_BSP11-03_Bukit SarangPlot 11, Bukit Lebik at Bukit Sarang, Bintulu, Sarawak.02°39.325'N, 113°02.432'E MG982280 MH033924
42 Georissa anyiensis sp. n. MZU/MOL 17.51 G.anyiensis_BSP11-04_Bukit SarangPlot 11, Bukit Lebik at Bukit Sarang, Bintulu, Sarawak.02°39.325'N, 113°02.432'E MG982279 MH033925
43 Georissa anyiensis sp. n. MZU/MOL 17.60 G.anyiensis_BSP22-01_Bukit SarangPlot 22, Bukit Anyi at Bukit Sarang, Bintulu, Sarawak.02°39.252'N, 113°02.723'E MG982272 n.a.
44 Georissa anyiensis sp. n. MZU/MOL 17.60 G.anyiensis_BSP22-02_Bukit SarangPlot 22, Bukit Anyi at Bukit Sarang, Bintulu, Sarawak.02°39.252'N, 113°02.723'E MG982273 MH033931
45 Georissa anyiensis sp. n. MZU/MOL 17.60 G.anyiensis_BSP22-03_Bukit SarangPlot 22, Bukit Anyi at Bukit Sarang, Bintulu, Sarawak.02°39.252'N, 113°02.723'E MG982274 MH033933
46 Georissa anyiensis sp. n. MZU/MOL 17.60 G.anyiensis_BSP22-04_Bukit SarangPlot 22, Bukit Anyi at Bukit Sarang, Bintulu, Sarawak.02°39.252'N, 113°02.723'E MG982275 MH033934
47 Georissa anyiensis sp. n. MZU/MOL 17.60 G.anyiensis_BSP22-05_Bukit SarangPlot 22, Bukit Anyi at Bukit Sarang, Bintulu, Sarawak.02°39.252'N, 113°02.723'E MG982276 MH033935
48 Georissa anyiensis sp. n. MZU/MOL 17.60 G.anyiensis_BSP22-06_Bukit SarangPlot 22, Bukit Anyi at Bukit Sarang, Bintulu, Sarawak.02°39.252'N, 113°02.723'E MG982277 MH033932
49 Georissa muluensis sp. n. MZU/MOL 17.31 G.muluensis_LGG-01_MuluPlot 1, Lagang Cave, Mulu National Park, Mulu, Sarawak.04°03.060'N, 114°49.372'E MG982288 MH033893
50 Georissa muluensis sp. n. MZU/MOL 17.31 G.muluensis_LGG-02_MuluPlot 1, Lagang Cave, Mulu National Park, Mulu, Sarawak.04°03.060'N, 114°49.372'E MG982285 MH033891
51 Georissa muluensis sp. n. MZU/MOL 17.31 G.muluensis_LGG-03_MuluPlot 1, Lagang Cave, Mulu National Park, Mulu, Sarawak.04°03.060'N, 114°49.372'E MG982286 MH033892
52 Georissa muluensis sp. n. MZU/MOL 17.31 G.muluensis_LGG-04_MuluPlot 1, Lagang Cave, Mulu National Park, Mulu, Sarawak.04°03.060'N, 114°49.372'E MG982287 MH033890
53 Georissa hadra Thompson & Dance, 1983 MZU/MOL 17.32 G.hadra_LC-01_MuluLang Cave, Mulu N.P., Mulu, Sarawak. 04°01.490'N, 114°49.482'E MG982284 MH033896
54 Georissa hadra Thompson & Dance, 1983 MZU/MOL 17.32 G.hadra_LC-02_MuluLang Cave, Mulu N.P., Mulu, Sarawak. 04°01.490'N, 114°49.482'E MG982282 MH033897
55 Georissa hadra Thompson & Dance, 1983 MZU/MOL 17.32 G.hadra_LC-03_MuluLang Cave, Mulu N.P., Mulu, Sarawak. 04°01.490'N, 114°49.482'E MG982281 MH033894
56 Georissa hadra Thompson & Dance, 1983 MZU/MOL 17.32 G.hadra_LC-04_MuluLang Cave, Mulu N.P., Mulu, Sarawak. 04°01.490'N, 114°49.482'E MG982283 MH033895
57 Georissa kobelti Gredler, 1902 MZU/MOL 17.36 G.kobelti_TC-01_NiahTrade Cave, Niah National Park, Niah, Sarawak. 03°49.137'N, 113°46.860'E MG982296 MH033886
58 Georissa kobelti Gredler, 1902 MZU/MOL 17.36 G.kobelti_TC-02_NiahTrade Cave, Niah National Park, Niah, Sarawak.03°49.137'N, 113°46.860'E MG982295 MH033889
59 Georissa kobelti Gredler, 1902 MZU/MOL 17.36 G.kobelti_TC-03_NiahTrade Cave, Niah National Park, Niah, Sarawak.03°49.137'N, 113°46.860'E MG982293 MH033887
60 Georissa kobelti Gredler, 1902 MZU/MOL 17.36 G.kobelti_TC-04_NiahTrade Cave, Niah National Park, Niah, Sarawak.03°49.137'N, 113°46.860'E MG982294 MH033888
61 Georissa kobelti Gredler, 1902 MZU/MOL 17.38 G.kobelti_KJ1-01_BaramPlot 1, Bukit Kaijin, Baram, Sarawak. 03°41.753'N, 114°27.555'E MG982290 MH033882
62 Georissa kobelti Gredler, 1902 MZU/MOL 17.38 G.kobelti_KJ1-02_BaramPlot 1, Bukit Kaijin, Baram, Sarawak. 03°41.753'N, 114°27.555'E MG982289 MH033883
63 Georissa kobelti Gredler, 1902 MZU/MOL 17.38 G.kobelti_KJ1-03_BaramPlot 1, Bukit Kaijin, Baram, Sarawak. 03°41.753'N, 114°27.555'E MG982292 MH033885
64 Georissa kobelti Gredler, 1902 MZU/MOL 17.38 G.kobelti_KJ1-04_BaramPlot 1, Bukit Kaijin, Baram, Sarawak. 03°41.753'N, 114°27.555'E MG982291 MH033884
65 Georissa niahensis Godwin-Austen, 1889 MZU/MOL 17.25 G.niahensis_PC-01_NiahPainted Cave, Niah National Park, Niah, Sarawak.03°48.688'N, 113°47.250'E MG982301 MH033965
66 Georissa niahensis Godwin-Austen, 1889 MZU/MOL 17.25 G.niahensis_PC-02_NiahPainted Cave, Niah National Park, Niah, Sarawak.03°48.688'N, 113°47.250'E MG982300 MH033878
67 Georissa niahensis Godwin-Austen, 1889 MZU/MOL 17.25 G.niahensis_PC-03_NiahPainted Cave, Niah National Park, Niah, Sarawak.03°48.688'N, 113°47.250'E MG982297 MH033877
68 Georissa niahensis Godwin-Austen, 1889 MZU/MOL 17.25 G.niahensis_PC-04_NiahPainted Cave, Niah National Park, Niah, Sarawak.03°48.688'N, 113°47.250'E MG982298 MH033954
69 Georissa niahensis Godwin-Austen, 1889 MZU/MOL 17.25 G.niahensis_GC-01_NiahPainted Cave, Niah National Park, Niah, Sarawak.03°48.688'N, 113°47.250'E MG982299 MH033879
70 Georissa niahensis Godwin-Austen, 1889 MZU/MOL 17.25 G.niahensis_GC-02_NiahPainted Cave, Niah National Park, Niah, Sarawak.03°48.688'N, 113°47.250'E MG982302 MH033880
71 Georissa niahensis Godwin-Austen, 1889 MZU/MOL 17.25 G.niahensis_GC-03_NiahPainted Cave, Niah National Park, Niah, Sarawak.03°48.688'N, 113°47.250'E MG982304 n.a.
72 Georissa niahensis Godwin-Austen, 1889 MZU/MOL 17.25 G.niahensis_GC-04_NiahPainted Cave, Niah National Park, Niah, Sarawak.03°48.688'N, 113°47.250'E MG982303 MH033881
73 Georissa silaburensis sp. n. MZU/MOL 17.05 G.silaburensis_SIG3-01_SilaburPlot 3, Gunong Silabur, Serian, Sarawak. 00°57.285'N, 110°30.228'E MG982323 MH033949
74 Georissa silaburensis sp. n. MZU/MOL 17.05 G.silaburensis_SIG3-03_SilaburPlot 3, Gunong Silabur, Serian, Sarawak. 00°57.285'N, 110°30.228'E MG982324 MH033948
75 Georissa silaburensis sp. n. MZU/MOL 17.05 G.silaburensis_SIG3-05_SilaburPlot 3, Gunong Silabur, Serian, Sarawak. 00°57.285'N, 110°30.228'E MG982325 MH033944
76 Georissa silaburensis sp. n. MZU/MOL 17.06 G.silaburensis_SIG4-01_SilaburPlot 4, Gunong Silabur, Serian, Sarawak. 00°57.285'N, 110°30.228'E MG982320 MH033945
77 Georissa silaburensis sp. n. MZU/MOL 17.06 G.silaburensis_SIG4-03_SilaburPlot 4, Gunong Silabur, Serian, Sarawak. 00°57.285'N, 110°30.228'E MG982321 MH033952
78 Georissa silaburensis sp. n. MZU/MOL 17.06 G.silaburensis_SIG4-06_SilaburPlot 4, Gunong Silabur, Serian, Sarawak. 00°57.285'N, 110°30.228'E MG982322 MH033951
79 Georissa silaburensis sp. n. MZU/MOL 17.07 G.silaburensis_SIG5-07_SilaburPlot 5, Gunong Silabur, Serian, Sarawak. 00°57.285'N, 110°30.228'E MG982316 MH033946
80 Georissa silaburensis sp. n. MZU/MOL 17.07 G.silaburensis_SIG5-08_SilaburPlot 5, Gunong Silabur, Serian, Sarawak. 00°57.285'N, 110°30.228'E MG982317 MH033950
81 Georissa silaburensis sp. n. MZU/MOL 17.07 G.silaburensis_SIG5-09_SilaburPlot 5, Gunong Silabur, Serian, Sarawak. 00°57.285'N, 110°30.228'E MG982318 n.a.
82 Georissa silaburensis sp. n. MZU/MOL 17.07 G.silaburensis_SIG5-10_SilaburPlot 5, Gunong Silabur, Serian, Sarawak. 00°57.285'N, 110°30.228'E MG982319 MH033947
83 Georissa bauensis sp. n. MZU/MOL 16.01 G.bauensis_B002_WCaveWind Cave Passage 3, Wind Cave National Park, Bau, Sarawak. 01°24.810'N, 110°08.175'E MG982306 MH033937
84 Georissa bauensis sp. n. MZU/MOL 16.01 G.bauensis_B003_WCaveWind Cave Passage 3, Wind Cave National Park, Bau, Sarawak. 01°24.810'N, 110°08.175'E n.a. MH033938
85 Georissa bauensis sp. n. MZU/MOL 16.01 G.bauensis_B004_WCaveWind Cave Passage 3, Wind Cave National Park, Bau, Sarawak. 01°24.810'N, 110°08.175'E MG982309 MH033936
86 Georissa bauensis sp. n. MZU/MOL 16.01 G.bauensis_B005_WCaveWind Cave Passage 3, Wind Cave National Park, Bau, Sarawak. 01°24.810'N, 110°08.175'E MG982307 n.a.
87 Georissa bauensis sp. n. MZU/MOL 16.01 G.bauensis_B007_WCaveWind Cave Passage 3, Wind Cave National Park, Bau, Sarawak. 01°24.810'N, 110°08.175'E MG982308 n.a.
88 Georissa bauensis sp. n. MZU/MOL 16.01 G.bauensis_B008_WCaveWind Cave Passage 3, Wind Cave National Park, Bau, Sarawak. 01°24.810'N, 110°08.175'E MG982311 MH033939
89 Georissa bauensis sp. n. MZU/MOL 16.01 G.bauensis_B009_WCaveWind Cave Passage 3, Wind Cave National Park, Bau, Sarawak.01°24.810'N, 110°08.175'E MG982305 n.a.
90 Georissa bauensis sp. n. MZU/MOL 16.01 G.bauensis_B010_WCaveWind Cave Passage 3, Wind Cave National Park, Bau, Sarawak.01°24.810'N, 110°08.175'E MG982310 n.a.
91 Georissa bauensis sp. n. MZU/MOL 16.03 G.bauensis_Q001_AyubGunong Podam, near Sg. Ayup, Kampung Bogag, Bau, Sarawak.01°21.158'N, 110°03.577'E MG982313 MH033942
92 Georissa bauensis sp. n. MZU/MOL 16.03 G.bauensis_Q002_AyubGunong Podam, near Sg. Ayup, Kampung Bogag, Bau, Sarawak.01°21.158'N, 110°03.577'E MG982312 n.a.
93 Georissa bauensis sp. n. MZU/MOL 16.03 G.bauensis_Q003_AyubGunong Podam, near Sg. Ayup, Kampung Bogag, Bau, Sarawak.01°21.158'N, 110°03.577'E MG982314 n.a.
94 Georissa bauensis sp. n. MZU/MOL 16.03 G.bauensis_Q004_AyubGunong Podam, near Sg. Ayup, Kampung Bogag, Bau, Sarawak.01°21.158'N, 110°03.577'E n.a. MH033941
95 Georissa bauensis sp. n. MZU/MOL 16.03 G.bauensis_Q005_AyubGunong Podam, near Sg. Ayup, Kampung Bogag, Bau, Sarawak.01°21.158'N, 110°03.577'E n.a. MH033940
96 Georissa bauensis sp. n. MZU/MOL 16.03 G.bauensis_Q006_AyubGunong Podam, near Sg. Ayup, Kampung Bogag, Bau, Sarawak.01°21.158'N, 110°03.577'E MG982315 MH033943
97 Georissa pyrrhoderma Thompson & Dance, 1983 MZU/MOL 17.11 G.pyrrhoderma_SO3-01_SilaburPlot Outside 3-1, Gunong Silabur, Serian, Sarawak.00°57.451'N, 110°30.207'E MG982366 MH033913
98 Georissa pyrrhoderma Thompson & Dance, 1983 MZU/MOL 17.11 G.pyrrhoderma_SO3-02_SilaburPlot Outside 3-1, Gunong Silabur, Serian, Sarawak.00°57.451'N, 110°30.207'E MG982364 MH033914
99 Georissa pyrrhoderma Thompson & Dance, 1983 MZU/MOL 17.11 G.pyrrhoderma_SO3-03_SilaburPlot Outside 3-1, Gunong Silabur, Serian, Sarawak.00°57.451'N, 110°30.207'E MG982367 MH033915
100 Georissa pyrrhoderma Thompson & Dance, 1983 MZU/MOL 17.11 G.pyrrhoderma_SO3-04_SilaburPlot Outside 3-1, Gunong Silabur, Serian, Sarawak.00°57.451'N, 110°30.207'E MG982365 MH033916
101 Georissa pyrrhoderma Thompson & Dance, 1983 MZU/MOL 17.22 G.pyrrhoderma_SIO4-01_SilaburPlot SIO4, Gunong Silabur, Serian, Sarawak. 00°57.451'N, 110°30.207'E MG982376 MH033918
102 Georissa pyrrhoderma Thompson & Dance, 1983 MZU/MOL 17.22 G.pyrrhoderma_SIO4-02_SilaburPlot SIO4, Gunong Silabur, Serian, Sarawak. 00°57.451'N, 110°30.207'E MG982377 MH033920
103 Georissa pyrrhoderma Thompson & Dance, 1983 MZU/MOL 17.22 G.pyrrhoderma_SIO4-03_SilaburPlot SIO4, Gunong Silabur, Serian, Sarawak. 00°57.451'N, 110°30.207'E MG982378 MH033917
104 Georissa pyrrhoderma Thompson & Dance, 1983 MZU/MOL 17.22 G.pyrrhoderma_SIO4-04_SilaburPlot SIO4, Gunong Silabur, Serian, Sarawak. 00°57.451'N, 110°30.207'E MG982379 MH033919
105 Georissa pyrrhoderma Thompson & Dance, 1983 MZU/MOL 17.22 G.pyrrhoderma_SIO4-05_SilaburPlot SIO4, Gunong Silabur, Serian, Sarawak. 00°57.451'N, 110°30.207'E MG982380 n.a.
106 Georissa pyrrhoderma Thompson & Dance, 1983 MZU/MOL 17.13 G.pyrrhoderma_SIE1-01_SilaburPlot SIE1, Gunong Silabur, Serian, Sarawak. 00°57.451'N, 110°30.207'E MG982372 n.a.
107 Georissa pyrrhoderma Thompson & Dance, 1983 MZU/MOL 17.13 G.pyrrhoderma_SIE1-02_SilaburPlot SIE1, Gunong Silabur, Serian, Sarawak. 00°57.451'N, 110°30.207'E MG982373 MH033922
108 Georissa pyrrhoderma Thompson & Dance, 1983 MZU/MOL 17.13 G.pyrrhoderma_SIE1-03_SilaburPlot SIE1, Gunong Silabur, Serian, Sarawak. 00°57.451'N, 110°30.207'E MG982374 MH033923
109 Georissa pyrrhoderma Thompson & Dance, 1983 MZU/MOL 17.13 G.pyrrhoderma_SIE1-04_SilaburPlot SIE1, Gunong Silabur, Serian, Sarawak. 00°57.451'N, 110°30.207'E MG982375 MH033921
110 Georissa pyrrhoderma Thompson & Dance, 1983 MZU/MOL 17.16 G.pyrrhoderma_SIE4-01_SilaburPlot SIE4, Gunong Silabur, Serian, Sarawak. 00°57.451'N, 110°30.207'E MG982368 MH033910
111 Georissa pyrrhoderma Thompson & Dance, 1983 MZU/MOL 17.16 G.pyrrhoderma_SIE4-02_SilaburPlot SIE4, Gunong Silabur, Serian, Sarawak. 00°57.451'N, 110°30.207'E MG982369 MH033909
112 Georissa pyrrhoderma Thompson & Dance, 1983 MZU/MOL 17.16 G.pyrrhoderma_SIE4-03_SilaburPlot SIE4, Gunong Silabur, Serian, Sarawak. 00°57.451'N, 110°30.207'E MG982370 MH033911
113 Georissa pyrrhoderma Thompson & Dance, 1983 MZU/MOL 17.16 G.pyrrhoderma_SIE4-04_SilaburPlot SIE4, Gunong Silabur, Serian, Sarawak. 00°57.451'N, 110°30.207'E MG982371 MH033912
114 Georissa kinabatanganensis sp. n. BOR/MOL 7289 G.kinabatanganensis_KPH01720.01_PangiKinabatangan Valley, Pangi, Sabah. 05°32.291'N, 118°18.376'E MG982348 MH033963
115 Georissa kinabatanganensis sp. n. BOR/MOL 7289 G.kinabatanganensis_KPH01720.02_PangiKinabatangan Valley, Pangi, Sabah. 05°32.291'N, 118°18.376'E MG982347 MH033962
116 Georissa kinabatanganensis sp. n. BOR/MOL 7289 G.kinabatanganensis_KPH01720.03_PangiKinabatangan Valley, Pangi, Sabah. 05°32.291'N, 118°18.376'E n.a. MH033961
117 Georissa kinabatanganensis sp. n. MZU/MOL 17.26 G.kinabatanganensis_K001_KeruakKeruak, near Kinabatangan river, Sandakan, Sabah. 05°32.291'N, 118°18.376'E MG982349 MH033959
118 Georissa kinabatanganensis sp. n. MZU/MOL 17.26 G.kinabatanganensis_K002_KeruakKeruak, near Kinabatangan river, Sandakan, Sabah.05°31.385'N, 118°17.113'E MG982351 MH033958
119 Georissa kinabatanganensis sp. n. MZU/MOL 17.26 G.kinabatanganensis_K005_KeruakKeruak, near Kinabatangan river, Sandakan, Sabah.05°31.385'N, 118°17.113'E MG982350 MH033960
120 Georissa sepulutensis sp. n. BOR/MOL 39 G.sepulutensis_KPH00176.01_SanaronSepulut Valley, Batu Sanaron, Sabah. 04°42.052'N, 116°36.016'E MG982357 MH033957
121 Georissa sepulutensis sp. n. BOR/MOL 39 G.sepulutensis_KPH00176.02_SanaronSepulut Valley, Batu Sanaron, Sabah. 04°42.052'N, 116°36.016'E MG982356 n.a.
122 Georissa sepulutensis sp. n. BOR/MOL 39 G.sepulutensis_KPH00181.01_SanaronSepulut Valley, Batu Sanaron, Sabah. 04°42.052'N, 116°36.016'E MG982359 MH033956
123 Georissa sepulutensis sp. n. BOR/MOL 12278 G.sepulutensis_Sca-002_PungitonSepulut Valley, Gua Pungiton, Sabah. 04°42.410'N, 116°36.040'E MG982361 MH033964
124 Georissa sepulutensis sp. n. BOR/MOL 12278 G.sepulutensis_Sca-003_PungitonSepulut Valley, Gua Pungiton, Sabah. 04°42.410'N, 116°36.040'E MG982360 MH033955
125 Georissa sepulutensis sp. n. BOR/MOL 12278 G.sepulutensis_Sca-004_PungitonSepulut Valley, Gua Pungiton, Sabah. 04°42.410'N, 116°36.040'E MG982362 MH033953
126 Georissa sepulutensis sp. n. BOR/MOL 12278 G.sepulutensis_Sca-005_PungitonSepulut Valley, Gua Pungiton, Sabah. 04°42.410'N, 116°36.040'E MG982363 n.a.
127 Georissa sepulutensis sp. n. BOR/MOL 39 G.sepulutensis_ZA004_SanaronSepulut Valley, Batu Sanaron, Sabah. 04°42.052'N, 116°36.016'E MG982354 n.a.
128 Georissa sepulutensis sp. n. BOR/MOL 39 G.sepulutensis_ZB003_SanaronSepulut Valley, Batu Sanaron, Sabah. 04°42.052'N, 116°36.016'E MG982355 n.a.
129 Georissa sepulutensis sp. n. BOR/MOL 39 G.sepulutensis_ZC003_SanaronSepulut Valley, Batu Sanaron, Sabah. 04°42.052'N, 116°36.016'E MG982358 n.a.
130 Georissa sepulutensis sp. n. RMNH/MOL 333905 G.sepulutensis_ZE003_SimbaluyonSepulut Valley, Bukit Simbaluyon, Sabah. 04°43.200'N, 116°34.140'E MG982352 n.a.
131 Georissa sepulutensis sp. n. RMNH/MOL 333905 G.sepulutensis_ZE004_SimbaluyonSepulut Valley, Bukit Simbaluyon, Sabah. 04°43.200'N, 116°34.140'E MG982353 n.a.
132 Georissa sepulutensis sp. n. BOR/MOL 39 (Schilthuizen et al., 2005) G.sepulutensis_hapA_AY547387_SanaronSepulut Valley, Batu Sanaron, Sabah. 04°42.052'N, 116°36.016'E AY547387 n.a.
133 Georissa sepulutensis sp. n. BOR/MOL 39 (Schilthuizen et al., 2005) G.sepulutensis_hapB_AY547388_SanaronSepulut Valley, Batu Sanaron, Sabah. 04°42.052'N, 116°36.016'E AY547388 n.a.

Sequence alignment and phylogenetic analyses

Sequence data and alignement. A total of 12 ingroup taxa of “scaly group” Georissa including an outgroup taxon, Georissa gomantongensis Smith, 1893, were used for phylogenetic analyses (using a much larger hydrocenid taxon sampling, to be published elsewhere, we confirmed that G. gomantongensis indeed branches off basally to the “scaly group”). We added another six 16S mtDNA sequences from GenBank, representing Georissa saulae (van Benthem-Jutting, 1966) (GenBank accession no. AY547380, AY547381, AY547384, and AY547385) and Georissa sepulutensis sp. n. (GenBank accession no. AY547387 and AY548388). We conducted our phylogenetic analyses based on 128 sequences for 16S and 91 sequences for CO1. The forward and reverse nucleotide reads were assembled using de novo Geneious 10.0.7 assembler, manually checked and edited, and later aligned using default settings of MUSCLE alignment (Edgar 2004). Phylogenetic inference. For CO1 sequences, we selected the invertebrate mitochondrial genetic code at the second reading frame. Ambiguous nucleotide sequence ends were trimmed and removed prior to further analysis. ModelFinder (Kalyaanamoorthy et al. 2017) was used to select the most appropriate model, based on the corrected Akaike Information Creterion (AICc) for partial 16S and CO1 mtDNA genes. The best fitting models were TIM3+F+I+G4 for 16S and TIM2+F+I+G4 for CO1. Phylogenetic analysis. Maximum likelihood analysis was performed using IQ-TREE 1.6.3 (Nguyen et al. 2014) on a concatenated 16S and CO1 sequences of “scaly” Georissa using TIM3+F+I+G4 as the nucleotide substitution models with ultrafast bootstrapping (1000 replicates) (Hoang et al. 2017). Bayesian Inference was performed using MrBayes 3.2.6 (Huelsenbeck and Ronquist 2001) with the next closest nucleotide substitution model, GTR+I+G using the following MCMC settings: Chain length = 1,100,000 generations, heated chain = 4, subsampling frequency = one tree for each 200 generations, burn-in length = 100,000, and chain temperature = 0.2.

Species delimitation and description

For species delimitation, we combined the data of molecular phylogenetic analyses and the assessments of the morphology. We aimed for monophyly in species, allowing paraphyly under certain circumstances (Schilthuizen and Gittenberger 1996), but disallowing polyphyly. Only when we found morphological characters that could distinguish DNA-based clades or paraphyletic groups, did we consider such groups as potential species. Although many forms in Georissa are allopatric, we did have a number of cases where two forms occurred sympatrically without forming intermediates, which also aided in determining species status by application of the biological species concept (Mayr 1942). General shell characters were further divided into detailed sub-characters exclusively for the descriptions of the representatives of the “scaly group” of Bornean Georissa. The assessed morphological characters follow the descriptions made by Godwin-Austen (1889), Gredler (1902), Haase and Schilthuizen (2007), Smith (1893, 1895), Thompson and Dance (1983), van Benthem-Jutting (1966), Vermeulen and Junau (2007), and Vermeulen et al. (2015). Note that color indications always refer to living or freshly dead specimens, as the color in older specimens usually degrades, with an exception for Georissa scalinella (van Benthem-Jutting, 1966), where only old collection specimens were available.

CO1 genetic divergence

In addition to the molecular phylogenetic and morphological assessment in our species delimitation, we conducted divergence analysis of partial CO1 genes to provide additional information to assist in the species delimitation of “scaly” Georissa. Several other studies on species delimitation in gastropods have also used CO1 mtDNA successfully (see Liew et al. 2014, Puillandre et al. 2012a, 2012b). Pairwise genetic distances of CO1 sequences from 89 individuals were computed based on Kimura 2-parameter with MEGA v. 7.0.26 (Kumar et al. 2016). These comprised of eleven species, including the six new species.

Web interface species delimitation using 16S mtDNA

We carried out two more approaches of web interface species delimitation to provide more insight in our species delimitation, namely, Automatic Barcode Gap Discovery (ABGD) (http://wwwabi.snv.jussieu.fr/public/abgd/abgdweb.html) (Puillandre et al. 2012a), and Poisson Tree Processes (PTP) (http://species.h-its.org/ptp/) (Zhang et al. 2013). ABGD analysis was carried out using 16S mtDNA sequences of the “scaly group” Georissa (excluding the outgroup). The parameters were set to default. For PTP analysis, we used the 16S gene tree generated from IQ-TREE (Nguyen et al. 2014). The parameters were set to default. Both ABGD and PTP analyses were conducted using mtDNA 16S sequences and gene tree based on the available data of all studied taxa. ABGD aims to partition the species based on the barcode gap (Puillandre et al. 2012a), while PTP focuses on the branching event of a rooted phylogenetic tree (Zhang et al. 2013).

Results and discussion

Morphology and phylogenetic analyses

Our morphological and phylogenetic studies lead us to conclude that there are at least 13 species of “scaly group” Georissa currently existing in Malaysian Borneo (for detailed morphological species descriptions, see the species treatments under the Taxonomy section). For one of these, Georissa scalinella (van Benthem-Jutting, 1966), DNA data are yet unavailable. Detailed conchological assessments of the “scaly group” show that at least two species, Georissa bauensis sp. n. and Georissa hosei Godwin-Austen, 1889, are highly variable (both intra- and inter-populationally) with regard to the “scaly” shell microsculpture characters (see Fig. 1). Due to the high inter- and intraspecific variation of these species, identification based on morphological characters alone could be problematic without prior knowledge of the shell variation within these species. Furthermore, species similar in shell habitus and scale characters, like Georissa pyrrhoderma Thompson & Dance, 1983 and Georissa sepulutensis sp. n., often have character combinations that overlap with either G. bauensis or G. hosei. Therefore, for identification of “scaly group” specimens, we found thorough conchological examination of the shells aided with molecular data is most reliable.

Figure 1. 

A–D Intraspecific variation in shell shape and sculpture of Georissa hosei Godwin-Austen, 1889 E–G Intraspecific variation in shell shape and sculpture of Georissa bauensis sp. n. H Georissa pyrrhoderma Thompson & Dance, 1983 I Georissa sepulutensis sp. n. For comparison with the “scaly group”, two additional species are shown that do not belong to the “scaly group”, namely: J Georissa gomantongensis Smith, 1893 and K Georissa nephrostoma Vermeulen et al., 2015. Localities: A, B Gunung Liak/Padang (Jambusan, Sarawak) C Bukit Siboyuh (Jambusan, Sarawak) D Bukit Tongak (Bau/Jambusan, Sarawak) E, F Gunung Podam (Bau, Sarawak) G Wind Cave Nature Reserve (Bau, Sarawak) H Gunung Silabur (Serian, Sarawak) I Batu Sanaron (Sanaron, Sabah) J Gua Gomantong (Gomantong, Sabah) K Keruak (Kinabatangan, Sabah). Scale bar 500 µm.

Based on the molecular phylogenetic analyses of the “scaly group” Georissa we find multiple strongly supported monophyletic groups (bootstrap and posterior output values ranging from 89–100 and 97–100, respectively) which correspond with subtly different conchologies. In contrast, Georissa kobelti Gredler, 1902 is paraphyletic, and we treat this as a single species based on the conchological characters that support they are conspecific.

CO1 genetic divergence

Despite geographic proximity for some populations of morphologically highly similar forms, the CO1 divergence analysis shows high genetic divergences (e.g. G. bauensis vs. G. hosei, genetic divergence = 0.12). For some other species, the interspecific genetic divergence is lower, but such species may be surprisingly distinct in shell sculpture (e.g. G. hadra vs. G. muluensis, genetic divergence = 0.07). As a consequence, we have sometimes given priority to genetic distinctness, sometimes to morphological distinctness in delimiting species, which means that intraspecific diversity may vary between species. For example, we found that G. pyrrhoderma, G. hosei, and G. kobelti are the three species to have the highest intraspecific divergence (0.06, 0.06 and 0.07, respectively) compared with the rest of the “scaly group”, where all other species have an intraspecific divergence equal to or lower than 0.05 (see details in Table 2). Our study reveals that within group divergences of “scaly” Georissa does not exceed 0.07 for each species, while the divergences between all species pairs exceed 0.10, with the exception of G. kinabatanganensis vs. G. sepulutensis, G. bauensis vs. G. silaburensis, G. hadra vs. G. muluensis and G. kobelti vs. G. niahensis.

Intra- and inter-specific CO1 sequence divergence of eleven species of “scaly” Georissa.

Divergence within group Number of specimens G. kinabatanganensis G. sepulutensis G. bauensis G. silaburensis G. anyiensis G. pyrrhoderma G. hosei G. hadra G. muluensis G. kobelti G. niahensis
1 G. kinabatanganensis 0.05 6
2 G. sepulutensis 0.02 5 0.06*
3 G. bauensis 0.03 8 0.11 0.14
4 G. silaburensis <0.01 9 0.12 0.13 0.04*
5 G. anyiensis 0.04 12 0.14 0.14 0.12 0.12
6 G. pyrrhoderma 0.06 15 0.10 0.11 0.11 0.11 0.09
7 G. hosei 0.06 11 0.14 0.13 0.12 0.12 0.10 0.12
8 G. hadra <0.01 4 0.18 0.18 0.16 0.15 0.12 0.15 0.14
9 G. muluensis <0.01 4 0.17 0.19 0.15 0.15 0.14 0.14 0.14 0.07*
10 G. kobelti 0.07 8 0.11 0.13 0.12 0.12 0.09 0.10 0.09 0.10 0.09
11 G. niahensis 0.04 7 0.13 0.15 0.13 0.14 0.10 0.12 0.10 0.11 0.13 0.05*

Web interface species delimitation using 16S mtDNA

To test to what extent automated procedures, based on genetic data alone, could reproduce our subjective species delimitation, we carried out ABGD and PTP analyses. ABGD recursive partition divided the “scaly group” Georissa into no more than six species at the lowest intraspecific divergence, while the highest divergence grouped all “scaly group” Georissa into a single species. The ABGD analysis further showed that partitioning into six species was due mostly to the separation of G. saulae into five different species while the rest of “scaly” Georissa were considered as a single species. This is possible due to the even higher intraspecific divergence of 16S mtDNA of G. saulae compared to the rest of “scaly group” taxa (see Suppl. material 2).

While ABGD analysis underestimated the number of possible species in the “scaly group” of Georissa, PTP analysis based on maximum likelihood delimitation results devided the taxa in at least 15 possible species. The results from this species delimitation method therefore more closely match our preferred approach (in which we combined phylogenetic and morphometric assessment). The PTP analysis does, however, differ from our preferred delimitation at several crucial points. G. saulae, G. kinabatanganensis, G. hosei, G. kobelti, and G. niahensis are each split into two species, whereas the two sets of species composed of (i) G. hadra and G. muluensis, and (ii) G. bauensis and G. silaburensis, are each considered as a single species, which make another two species. Otherwise, PTP analysis resolves the same species as in our preferred resolution (see Suppl. material 3).

The results from CO1 barcoding, ABGD, and PTP analyses reveal that objective species delimitation based solely on molecular data will not be successful for “scaly group” Georissa, at least if one wishes for the taxonomy to reflect morphology as well. Since most species are allopatric, and therefore the maintenance of species barriers can usually not be tested, we present our taxonomy as a compromise, which remains to be further tested by future workers.

Taxonomy

Systematics and descriptions

Class Gastropoda Cuvier,1797

Family Hydrocenidae Troschel, 1856

Genus Georissa Blanford, 1864: 463
“Scaly group”

We here define an informal group of 13 species of Georissa from Malaysian Borneo that are characterised by one or more spiral rows of scale-like sculptures. As far as they were known at the time, our “scaly group” corresponds to Thompson and Dance’s (1983)hosei group” + “borneensis group” p.p.

Conchological description of a generalised “scaly group” representative. Protoconch. Color (in living or freshly dead specimens): yellow, orange, red or brown. Sculpture: smooth, meshed, mixed or undefined. Teleoconch. Color (in living or freshly dead specimens): yellow, orange, red or brown. First whorl: convex, rounded to flat or angular. Subsequent whorls: convex, rounded, concave or tilted at the periphery, or flat, with well-impressed suture. Number of whorls: 2–3 ¼. Shell height (SH) (based on our conchological measurements of available studied materials stated in the methodology): 0.94–2.91 mm. Shell width (SW): 0.98–2.19 mm. Shell index (SI=SH/SW): 0.88-1.37. Shell sculpture. Radial sculpture: either absent or present. Growth lines: weak to strong. Spiral sculpture: absent or present; if present then weakly to strongly sculpted, continuous or discontinuous. Scales: between one and four spiral rows of vertical scales (any one of which may be more or less strongly pronounced than the others); scales can be minute to broad, low to acutely projecting. Columella wall. Smooth, translucent, and covering the umbilicus region. Aperture. Shape: oval to rounded, with straight to concave or convex parietal site, palatal edge either contiguous with or removed from the body whorl. Aperture height (AH): 0.50–1.33 mm. Aperture width (AW): 0.69–1.48 mm. Aperture index (AI=AH/AW): 0.65–1.02. Peristome. Simple, thickened inside, sharp toward the edge of the aperture. Operculum. Oval to rounded, with a peg facing inward, inner surface of the operculum has a small crater-like hole. Peg: straight or curved. The shell measurement of all measured “scaly group” Georissa are summarised in Suppl. material 4.

Anatomy. Haase and Schilthuizen (2007) described the anatomy of two closely related Georissa, viz. G. saulae and G. filiasaulae, and noted interspecific differences in radula, genital anatomy. Anatomical details of other “scaly group” representatives will be the focus of future studies and are not included in the present review.

Habitat and ecology. Members of the “scaly group” of Georissa live on limestone rocks, especially in wet and shaded environments. They are also found at lower density on dry limestone rocks, and occasionally on the limestone walls in cave systems (Haase and Schilthuizen 2007).

Distribution. There are at least nine species of this group distributed in Sarawak, and another four are distributed in Sabah (see Figs 3 and 4). In the distribution maps, we combined the geographical coordinates of each species from the known previous fieldwork locations and the available data from the collection repositories. The distribution of “scaly group” Georissa was assigned based on the available locality data from the collection from NHMUK, RMNH, ZMA, BOR, ZMU, and JJV. Localities may contain Malay words, namely: Batu = rock; Bukit = hill; Gua = cave; Gunung = mountain. We provide two distribution maps (Figs 3 and 4) to avoid overlapping of species that co-occur at the same or nearby locations.

In the following systematic descriptions of “scaly” Georissa, the species are arranged based on the molecular phylogeny. Georissa scalinella (van Benthem-Jutting, 1966), for which no genetic data are available, is placed at the top of the list.

For the stacked images of the “scaly” Georissa (Figs 517A–C), we decided not to remove the periostracum layers of the shells to retain the morphological characters of each species.

Since we needed fresh material to connect the morphology and molecular phylogenetics, we confined our study to Malaysian part of Borneo. We are aware that there might be species or populations in other parts of Borneo (Kalimantan, Indonesian Borneo and Brunei) which belong inside the “scaly group”. However, we hope that our study will stimulate colleagues that study Georissa in Kalimantan or Brunei to compare their material with our analysis.

Figure 2. 

A Phylogeny from ML analysis with ultrafast bootstrapping (1000 replicates) B Phylogeny from MrBayes analysis. Analyses were conducted using concatenated sequence alignments of partial CO1 and 16S mtDNA of 133 individuals of “scaly” Georissa from Malaysian Borneo, with Georissa gomantongensis Smith, 1893 as the outgroup.

Figure 3. 

Distribution of seven “scaly group” Georissa species in Malaysian Borneo (based on the materials examined from NHM, RMNH, ZMA, BORN, MZU, and JJV).

Figure 4. 

Distribution of five “scaly group” Georissa species in Malaysian Borneo (based on the materials examined from NHM, RMNH, ZMA, BORN, MZU, and JJV).

Georissa scalinella (van Benthem-Jutting, 1966)

Hydrocena scalinella van Benthem-Jutting, 1966: 39, fig. 1; Saul 1967: 108.

Georissa scalinella (van Benthem-Jutting): Thompson and Dance 1983: 119; Phung et al. 2017: 68, fig. 8B.

Type locality

Lahad Datu Caves on Teck Guan Estate, Sabah.

Type material

Holotype. Lahad Datu Caves on Teck Guan Estate, Sabah: ZMA/MOLL 135736 (seen). Paratypes. Lahad Datu Caves on Teck Guan Estate, Sabah: ZMA/MOLL 135735 (seen), ZMA/MOLL 315596 (seen).

Description

Protoconch. Color: orange to red. Sculpture: smooth to meshed – semi oval mesh to undefined mesh pattern. Mesh width: 7–17 µm. Teleoconch. Color: orange. First whorl: flat at the shoulder. Subsequent whorls: flat above, slightly rounded below the periphery. Total number of whorls: 2 ¼-2 ½. SH: 1.56–1.80 mm, SW: 1.46–1.65 mm, SI: 1.03–1.15. Shell sculpture. Radial sculpture: absent, only weak to strong growth lines are visible. Spiral sculpture: present, and strongly sculpted, with continuous and discontinuous ribbing. Scales: a series of acute scales, low to highly projected, and regularly spaced. Intercept between growth lines and spiral ribbings form small pointed scale structures throughout the length of the body whorl. Aperture. Shape: oval. Basal side: rounded, angular at the columellar region. Parietal side: straight, palatal edge attached to the body whorl. AH: 0.78–0.94 mm, AW: 0.97–1.12 mm, AI: 0.75–0.89. Holotype dimension. SH: 1.88 mm, SW: 1.72 mm, AH: 0.84 mm, AW: 1.18 mm.

Figure 5. 

Georissa scalinella (van Benthem-Jutting, 1966). A–C Holotype: ZMA/MOL/ 135736 D–K Paratypes: ZMA/MOLL 135735. A, D Shell apertural view B Shell side view C Shell rear view E–F Shell cross-section from 3D model G–H Operculum frontal and ventral view I Shell top view J Protoconch side view K Close up of protoconch from top at 1000× magnification. Scale bars: 500 µm (A–I); 200 µm (J); 10 µm (K).

Cross diagnosis

Georissa scalinella has a series of scales at the shoulder. In habitus and scale characters, it resembles G. pyrrhoderma from Gunung Silabur, Sarawak. The angular shoulder and small scale-like nodular structure at the intersection of strong spiral ribbings and growth lines are diagnostic for G. scalinella.

Distribution

Known only from the type locality, Teck Guan Estate, Lahad Datu, Sabah, and also reported by Phung et al. (2017) at Pulau Tiga, Sandakan, Sabah. However, this may also refer to one of the other “scaly group” species from Sabah.

Discussion

Georissa scalinella was first described as Hydrocena scalinella van Benthem-Jutting, 1966, before reclassified as Georissa by Thompson and Dance (1983). van Benthem-Jutting (1966) described G. scalinella as having strong spiral ribbing and multiple lines of scales.

Georissa saulae (van Benthem-Jutting, 1966)

Hydrocena saulae van Benthem-Jutting, 1966: 40, fig. 2; Saul 1967: 109.

Georissa saulae (van Benthem-Jutting): Thompson and Dance 1983: 118, fig. 29, 53–54; Haase and Schilthuizen 2007: 217, fig. 2; Clements 2008: 2762; Schilthuizen et al. 2012: 278; Beron 2015: 181; Phung et al. 2017: 68, fig. 8; Osikowski et al. 2017: 80.

Type locality

Malaysia, Borneo, Sabah, Laying cave, Keningau.

Type material

Holotype. Malaysia, Borneo, Sabah, Laying cave, Keningau: ZMA/MOLL 135731 (seen). Paratypes. Malaysia, Borneo, Sabah, Laying cave, Keningau: ZMA/MOLL 135598 (seen), ZMA/MOLL 135599 (seen).

Other material

Simbaluyon limestone hill, Sabah, Malaysia: RMNH/MOL 333913, RMNH/MOL 333919. Crocker Range National Park, Gua Laing, Keningau, Sabah (05°29.00'N, 116°08.00'E): RMNH/MOL 335180, ZMA/MOLL 315592, ZMA/MOLL 315593, JJV 1119. Sepulut Valley, Gua Pungiton, Sabah (04°42.41'N, 116°36.04'E): BOR/MOL 28, BOR/MOL 12770, JJV 7544. Sepulut valley, Gua Sanaron, Sabah (04°42.05'N, 116°36.01'E): BOR/MOL 29, BOR/MOL 32, BOR/MOL 3493, JJV 7660. Pinangah valley, Batu Urun (Bukit Sinobang), Sabah (04°48.40'N, 116°37.35'E): BOR/MOL 31, JJV 1144, JJV 5632, JJV 7993. Mahua, Sabah: BOR/MOL 33. Pun Batu, Sepulut, Sabah (04°45.00'N, 116°10.00'E): JJV 1268. Sepulut valley, Batu Punggul, Sabah: JJV 1904.

Description

Protoconch. Color: red to brown. Sculpture: meshed – ellipsoidal mesh pattern. Mesh width: 29–54 µm. Teleoconch. Color: brown to red. First whorl: convex to rounded. Subsequent whorls: convex to rounded. SH: 1.32–1.86 mm, SW: 1.14–1.48 mm, SI: 1.12–1.26. Total number of whorls: 2 ½-3 ¼. Shell sculpture. Radial sculpture: often present, when formed by vertical connections between corresponding scales on successive spiral ribs. These vertical connections, especially on the first whorls, form evenly spaced ribs that are raised when crossing a spiral rib. Spiral sculpture: present at the early teleoconch, subsequently becoming weaker, and later only short discontinuous lines are visible in between the radial sculptures. Scales: usually three or four discontinuous series of vertical, low to high-projecting scales, broad to pointed (only if the spiral series of scales are discontinuous). Aperture. Shape: rounded to slightly oval. Basal side: rounded, slightly angular before the columellar region. Parietal side: straight, connected to the palatal edge. AH: 0.58–0.83 mm, AW: 0.70–0.94 mm, AI: 0.76–0.92. Holotype dimension. SH: 1.60 mm, SW: 1.28 mm, AH: 0.66 mm, AW: 0.80 mm.

Figure 6. 

Georissa saulae (van Benthem-Jutting, 1966). A–C Holotype: ZMA/MOL 135599 D–K BOR/MOL 3493. A, D Shell apertural view B Shell side view C Shell rear view E–F Shell cross-section from 3D model G–H Operculum frontal and ventral view I Shell top view J Protoconch side view K Close up of protoconch from top at 1000× magnification. Scale bars: 500 µm (A–I); 200 µm (J); 10 µm (K).

Cross diagnosis

Georissa saulae possesses clear diagnostic shell characters for distinction from other “scaly” Georissa species. G. saulae lacks a clear formation of spiral ribbing: although the spiral arrangement of the scales gives the impression of spiral sculpture, no underlying ribs are discernable. G. scalinella, G. kinabatanganensis, and G. hosei, on the other hand, have clear diagnostic spiral ribs. The shell whorls of G. saulae are broad but not as rapidly expanding as in G. hosei, G. scalinella or G. kinabatanganensis. It can also be distinguished from G. scalinella and G. hosei on the basis of a more elongate-conical shell shape and the aperture shape that is more rounded rather than oval.

Distribution

The type locality of Georissa saulae is Laying cave, in the Crocker Range, Keningau, Sabah (a misspelling of Laing cave). Otherwise known from limestone outcrops in Sabah’s interior, viz., Simbaluyon, Sinobang, Sanaron, and Pungiton, and also has been recorded from Mahua, Sabah, which is not a limestone area. Phung et al. (2017) also report it from Pulau Tiga, Sabah.

Molecular analysis

ML and Bayesian analyses show Georissa saulae (16S: n = 11) as a monophyletic group with 100% BS and 100% PP. Schilthuizen et al. (2012) reported that G. saulae is a paraphyletic group from which emerges the cave-dwelling species G. filiasaulae (Haase and Schilthuizen 2007), a fully unsculptured species that was not included in the present study. G. saulae + G. filiasaulae are sister to all other species in the “scaly group” (unpublished data).

Discussion

Georissa saulae was initially described as Hydrocena saulae van Benthem-Jutting, 1966, then assigned to the genus Georissa by Thompson and Dance (1983). Thompson and Dance (1983) compared G. saulae with G. scalinella, and even suggested G. saulae might be a subspecies. In contrast, we find that G. saulae is a proper species with very distinct conchological characters, especially the presence of radial ribs on the shell, which makes it easy to identify. In some specimens from the entrance of the Batu Sanaron cave system, the vertical scales are spaced, and radial sculpture is weak. Such individuals presumably represent the hybrid zone with the cave-dwelling G. filiasaulae (Haase and Schilthuizen 2007, Schilthuizen et al. 2012).

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.

Figure 7. 

Georissa hosei Godwin-Austen, 1889. A–C MZU/MOL 16.05 D–K MZU/MOL 16.04. A, D Shell apertural view B Shell side view C Shell rear view E–F Shell cross-section from 3D model G–H Operculum frontal and ventral view I Shell top view J Protoconch side view K Close up of protoconch from top at 1000× magnification. Scale bars: 500 µm (A–I); 200 µm (J); 10 µm (K).

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.

Georissa anyiensis sp. n.

Georissa hosei Godwin-Austen: Thompson and Dance 1983: 117, materials from Tatau Valley, Bukit Sarang, Bintulu, Sarawak. (nonG. 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.

Etymology

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

Description

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.

Figure 8. 

Georissa anyiensis sp. n. A–C Holotype: MZU/MOL 17.90 D–K Paratypes: MZU/MOL 17.55. A, D Shell apertural view B Shell side view C Shell rear view E–F Shell cross-section from 3D model G–H Operculum frontal and ventral view I Shell top view J Protoconch side view K Close up of protoconch from top at 1000× magnification. Scale bars: 500 µm (A–I); 200 µm (J); 10 µm (K).

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.

Distribution

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.

Georissa muluensis sp. n.

Type locality

Lagang Cave, Mulu National Park, Mulu, Sarawak, Malaysia (04°03.06'N, 114°49.37'E).

Type material

Holotype. Lagang Cave, Mulu National Park, Mulu, Sarawak, Malaysia (04°03.06'N, 114°49.37'E): MZU/MOL 17.86 (leg. MZ Khalik and SK Reduan). Paratypes. Lagang Cave, Mulu National Park, Mulu, Sarawak (04°03.06'N, 114°49.37'E): MZU/MOL 17.30 (13), MZU/MOL 17.31 (9).

Other material

Deer Cave, Mulu National Park, Mulu, Sarawak: JJV 10533 (this sample, approximately 120 individuals, also contains specimens of G. hadra), JJV 10554 (this sample contains 5 individual of G. muluensis, 1 individual G. hadra), JJV 10533 (this sample, approximately 150 individuals, also contains specimens of G. hadra and G. kobelti). Mulu N.P., Mulu, Sarawak: JJV 10527.

Etymology

Named after Mulu National Park, Sarawak, Malaysia, the type locality.

Description

Protoconch. Color: yellow. Sculpture pattern: meshed – ellipsoidal mesh shape. Mesh width: 16–26 µm. Teleoconch. Color: yellow. First whorl: shouldered, above the shoulder flat, nearly horizontal; below the shoulder flat, cylindrical, but abruptly withdrawn into the deeply incised suture. Subsequent whorls: convex to rounded. SH: 1.67–2.05 mm, SW: 1.57–1.79 mm, SI: 1.08–1.18. Total number of whorls: 2 ¼-3. Shell sculpture. Radial sculpture: absent, only weak to strong growth lines are visible. Spiral sculpture: present, consisting of thin, but strongly sculpted and continuous ribs. Scales: two to three series of tall and diagonal scales, regularly spaced, the upper scale series always stronger than the lower ones, weaker series appear later at the spire or consist only of randomly spaced arrays of acute nodules, widely spaced between the first and second scale series, more densely spaced later. Aperture. Shape: rounded to slightly oval. Basal side: rounded, angular at the columellar region. Parietal side: straight to slightly curved. AH: 0.82–0.98 mm, AW: 1.03–1.18 mm, AI: 0.77–0.83. Holotype dimension. SH: 1.67 mm, SW: 1.53 mm, AH: 0.82 mm, AW: 1.07 mm.

Figure 9. 

Georissa muluensis sp. n. A–C Holotype: MZU/MOL 17.86 D–K Paratypes: MZU/MOL 17.30. A, D Shell apertural view B Shell side view C Shell rear view E–F Shell cross-section from 3D model G–H Operculum frontal and ventral view I Shell top view J Protoconch side view. K. Close up of protoconch from top at 1000× magnification. Scale bars: 500 µm (A–I); 200 µm (J); 10 µm (K).

Cross diagnosis

The wide spacing of the major spiral scale series of G. muluensis is similar to G. kinabatanganensis, but G. muluensis has a more elongated shell shape, rather than the more flattened habitus of G. kinabatanganensis. In general shell shape and sculpture G. muluensis also resembles G. hadra, which, however, is larger and more elongated.

Distribution

Known only from the small area of Lagang Cave, Mulu National Park, Mulu, Sarawak, Malaysia.

Molecular analysis

ML and Bayesian analyses show that the individuals of G. muluensis (16S: n = 4; CO1: n = 4) form a monophyletic group with 100% BS and 100% PP, which is the sister group of G. hadra.

Georissa hadra Thompson & Dance, 1983

Georissa hadra Thompson & Dance, 1983: 115–116, fig. 32, 43–46.

Type locality

Butik Besungai, a small limestone hill 0.5 miles southwest of Batu Gading, and about 4 miles northeast of Long Lama, Baram Valley, Fourth Division, Sarawak. 03°52'N, 114°25'E.

Type material

Holotype. Butik Besungai, a small limestone hill 0.5 miles southwest of Batu Gading, and about 4 miles northeast of Long Lama, Baram Valley, Fourth Division, Sarawak: UF36107 (not seen). Paratypes. Butik Besungai ½ mile SW. of Batu Gading, 4 miles NE. of Long Lama, Baram Valley, 4th Div., Sarawak, Malaysia: BMNH 1984004 (seen). Baram valley, Long Lama, Bt. Besungai 0.5 m SW of Batu Gading, Sarawak (03°52.00'N, 114°25.00'E): JJV 13421 (seen).

Other material

Lang Cave, Mulu N.P., Mulu, Sarawak (04°01.49'N, 114°49.48'E): MZU/MOL 17.32, MZU/MOL 17.33, MZU/MOL 17.34, MZU/MOL 17.35. Deer Cave, Mulu N.P., Mulu, Sarawak: JJV 10533 (this sample, approximately 120 individuals, also contains G. muluensis), JJV 10554 (5 individual of G. muluensis, 1 individual G. hadra), JJV 10533 (this sample, approximately 150 individuals, also contains G. muluensis and G. kobelti).

Butik = a misspelling of Bukit, a local name for hill.

Description

Protoconch. Color: orange. Sculpture pattern: meshed – rounded to ellipsoidal or undefined mesh shape. Mesh width: 12–24 µm. Teleoconch. Color: orange. First whorl: with a distinct shoulder (provided with a series of minuscule scales), above the shoulder flat and tapering towards the suture, below the shoulder flat and cylindrical. Subsequent whorls: distinctly scalariform, with three separate aspects separated by two or more main spiral series of scales: above the uppermost spiral series gently curved towards the suture; in between both spiral series flat and cylindrical; below the lowest spiral series abruptly narrowed towards the deeply impressed suture (on the final whorl these three aspects fuse, forming a uniformly rounded impression). SH: 2.61–2.91 mm, SW: 2.05–2.19 mm, SI: 1.21–1.37. Total number of whorls: 2 ¾-3 ¼. Shell sculpture. Radial sculpture: absent, but with strong and unevenly layered growth lines. Spiral sculpture: present, weakly sculpted, continuous to discontinuous. Scales: two to four irregularly spaced series of low to high, and minute to broad diagonal scales, densely spaced, the first scale series always the strongest, weaker series appearing later at the spire. Aperture. Shape: rounded, with a tilt below the palatal side. Basal side: rounded, angular at the columellar region. Parietal side: straight to curved. AH: 1.11–1.33 mm, AW: 1.32–1.48 mm, AI: 0.83–1.01.

Figure 10. 

Georissa hadra Thompson & Dance, 1983. A–C MZU/MOL 17.33 D–K ZMA/MOLL 17.32. A, D Shell apertural view B Shell side view C Shell rear view E–F Shell cross-section from 3D model G–H Operculum frontal and ventral view I Shell top view J Protoconch side view K Close up of protoconch from top at 1000× magnification. Scale bars: 1 mm (A–I); 200 µm (J); 10 µm (K).

Cross diagnosis

Georissa hadra has scales which are densely arranged, unlike G. scalinella, G. hosei, G. muluensis, G. anyiensis, and G. kobelti, which have more widely spaced scales. In shell shape, G. hadra is similar to the later three species but larger and more distinctly scalariform. G. hadra is similar in size to G. niahensis, but it has a more slender habitus and a more rounded periphery.

Distribution

The type locality for G. hadra is Bukit Besungai, Baram, Sarawak. We also obtained it at Mulu, Sarawak. Currently, therefore, the known distribution range is restricted to Mulu and Baram.

Molecular analysis

ML and Bayesian analyses retrieve G. hadra (16S: n = 4; CO1: n = 4) as a single clade with 89% BS and 100% PP, sister to G. muluensis.

Discussion

The paratypes of Thompson and Dance (1983) have a very pale orange color, compared to recently collected materials from Mulu; presumably the color has faded.

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 (nonG. 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).

Description

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.

Figure 11. 

Georissa kobelti Gredler, 1902. A–C MZU/MOL 17.40 D–K MZU/MOL 17.38. A, D Shell apertural view B Shell side view C Shell rear view E–F Shell cross-section from 3D model G–H Operculum frontal and ventral view I Shell top view J Protoconch side view K Close up of protoconch from top at 1000× magnification. Scale bars: 500 µm (A–I); 200 µm (J); 10 µm (K).

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.

Distribution

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.

Georissa niahensis Godwin-Austen, 1889

Georissa niahensis Godwin-Austen, 1889: 353; Thompson and Dance 1983: 119.

Type locality

Niah Hills, Borneo. (Unspecified)

Type material

Lectotype (Designated by Thompson and Dance 1983). Niah Hills, Borneo: NHMUK 1889.12.7.69 (glued on paper) (seen). Paralectotype. Niah Hills, Borneo: NHMUK 1889.12.7.70 (glued on paper) (seen).

Other material

Painted Cave, Niah National Park, Niah, Sarawak (03°48.68'N, 113°47.25'E): MZU/MOL 17.25.

Description

Protoconch. Color: red. Sculpture pattern: smooth and meshed – ellipsoid to irregular mesh shape. Mesh width: 12–19 µm. Teleoconch. Color: orange to red. First whorl: curved above the shoulder, flat and cylindrical below the shoulder. Subsequent whorls: convex, angular at the periphery. SH: 1.81–2.53 mm, SW: 1.51–1.99 mm, SI: 1.10–1.29. Total number of whorls: 3–3 ¼. Shell sculpture. Radial sculpture: absent, only strong and unevenly layered growth lines. Spiral sculpture: present, strongly sculpted, continuous to discontinuous, well defined from the first whorl all the way to the peristome. Scales: a single spiral series of low and minute acute scales, regularly spaced at the first whorl, but weaker, grading to imperceptible on the body whorl. Aperture. Shape: rounded. Basal side: rounded, angular at the columellar region. Parietal side: straight to curved. AH: 0.85–1.24 mm, AW: 0.92–1.27 mm, AI: 0.83–1.02.

Figure 12. 

Georissa niahensis Godwin-Austen, 1889. A–K MZU/MOL 17.25 A, D Shell apertural view B Shell side view C Shell rear view E–F Shell cross-section from 3D model G–H Operculum frontal and ventral view I Shell top view J Protoconch side view K Close up of protoconch from top at 1000× magnification. Scale bars: 1 mm (A–I); 200 µm (J); 10 µm (K).

Cross diagnosis

Georissa niahensis has a distinctive single series of small scales on the whorl shoulder, close to the suture. G. niahensis is one of the largest Bornean Georissa, in shell size only matched by G. hadra (which, however, is more slender, angular at the shoulder and has a flat to slightly rounded whorls). In general shell shape, G. niahensis is closest to G. kobelti, but the latter species is more rounded, while G. niahensis has a distinctly convex periphery.

Distribution

Known to occur only at Niah, Sarawak.

Molecular analysis

ML and Bayesian analyses of G. niahensis (16S: n = 8; CO1: n = 7) showed that all G. niahensis specimens form one clade with 100% BS and 100% PP. The sister group is the G. kobelti population from Baram (G. kobelti is paraphyletic).

Discussion

Both Godwin-Austen (1889) and Thompson and Dance (1983) did not mention anything about the small scale-like nodules close to the suture of G. niahensis. Godwin-Austen (1889): “Shell elongately conoid, solid, imperforate; sculpture a very in-distinct, ill-defined spiral liration, about 20 on the penultimate whorl, upon a rough surface crossed by transverse lines of growth; color ruddy ochre; spire high; apex pointed, finely papillated, minutely lirate; suture impressed; whorls 4 ½ convex; aperture oval, oblique; peristome simple, acute below; columellar margin straight”. Thompson and Dance (1983): “G. niahensis is similar in sculpture to G. williamsi but is much larger. G. niahensis also shows similarities to the hosei group in the depth of the suture and the relatively rapid expanding whorls, but it lacks the node-like sculpture found among species of that group.” The scales are relatively small which are not very conspicuous among the strong growth lines, and this is the reason why in the previous description of the species the scale characters were lacking. Thompson and Dance (1983) compared G. niahensis with what they call the hosei group, based on the size and the deeply impressed suture.

Georissa silaburensis sp. n.

Type locality

Gunong Silabur, Serian, Sarawak, Malaysia (00°57.28'N, 110°30.22'E).

Type material

Holotype. Gunong Silabur, Serian, Sarawak, Malaysia (00°57.28'N, 110°30.22'E): MZU/MOL 17.88 (leg. MZ Khalik and SK Reduan). Paratypes. Gunong Silabur, Serian, Sarawak, Malaysia (00°57.28'N, 110°30.22'E): MZU/MOL 17.01, MZU/MOL 17.02, MZU/MOL 17.03, MZU/MOL 17.04, MZU/MOL 17.05, MZU/MOL 17.06, MZU/MOL 17.07, MZU/MOL 17.08. Borneo, Sarawak, First Division, western side of Gunong Selabor, Semabang entrance to Lobang Batu Cave (00°55'N, 110°25'E): NHMUK 1984005 (seen). Each lot of examined paratypes from MZU are more than 50 individuals.

Etymology

Named after Gunung Silabur, Serian, Sarawak, Malaysia, the type locality.

Description

Protoconch. Color: red. Sculpture pattern: meshed – round to irregular mesh pattern. Mesh width: 8–18 µm. Teleoconch. Color: red. First whorl: rounded. Subsequent whorls: convex, number of whorls: 2–2 ¼. SH: 1.59–1.99 mm, SW: 1.50–1.76 mm, SI: 1.06–1.13. Shell sculpture. Radial sculpture: absent or weak to strong growth lines. Spiral sculpture: present, thin but strongly sculpted, continuous ribs, more prominent at the periphery. Scales: two to six or more randomly sculpted series of low and broad horizontal scales, or else acute horizontal nodules on the spiral sculpture, scale series irregularly spaced, which series is the most prominent is not consistent across individuals. Aperture. Shape: rounded. Basal side: rounded, angular at the columellar region. Parietal side: straight, palatal edge attached to slightly removed from the body whorl. AH: 0.95–1.09 mm, AW: 1.00–1.17 mm, AI: 0.92–0.99. Holotype dimension. SH: 1.68 mm, SW: 1.53 mm, AH: 0.95 mm, AW: 1.09 mm.

Figure 13. 

Georissa silaburensis sp. n. A–C Holotype: MZU/MOL 17.88 D–K Paratypes: MZU/MOL 17.04. A, D Shell apertural view B Shell side view C Shell rear view E–F Shell cross-section from 3D model G–H Operculum frontal and ventral view I Shell top view J Protoconch side view K Close up of protoconch from top at 1000× magnification. Scale bars: 500 µm (A–I); 200 µm (J); 10 µm (K).

Cross diagnosis

The shell shape of G. silaburensis is distinct compared to other “scaly group” Georissa. It has rapid shell expansion like G. hosei and G. scalinella, but G. silaburensis has a different sculpture, consisting of horizontal, rather than vertical or diagonal scales. In addition, the whorls are rounded and convex, with the aperture almost circular, close to G. saulae.

Distribution

Known from the inside of the cave system of Gunung Silabur, Serian, Sarawak.

Molecular analysis

ML and Bayesian analyses show that the individuals of G. silaburensis (16S: n = 10; CO1: n = 9) form one clade with 95% BS and 98% PP, the sister group of G. bauensis.

Discussion

Georissa silaburensis was only found inside the cave entrance, with water flowing from the cave roof, and approximately less than 50% light penetration. In shell shape and reduced sculpture, it resembles another cave specialist, G. filiasaulae.

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.

Figure 14. 

Georissa bauensis sp. n. A–C Holotype: MZU/MOL 17.89 D–K Paratypes: MZU/MOL 16.03. A, D Shell apertural view B Shell side view C Shell rear view E–F Shell cross-section from 3D model G–H Operculum frontal and ventral view I Shell top view J Protoconch side view K Close up of protoconch from top at 1000× magnification. Scale bars: 500 µm (A–I); 200 µm (J); 10 µm (K).

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.

Georissa pyrrhoderma Thompson & Dance, 1983

Georissa pyrrhoderma Thompson & Dance, 1983: 123, fig. 64.

Georissa pyrrhoderma van Benthem-Jutting, in Beron 2015: 181.

Type locality

Borneo, Sarawak, First Division, western side of Gunong Selabor, Semabang entrance to Lobang Batu Cave (00°55'N, 110°25'E).

Type material

Holotype. Borneo, Sarawak, First Division, western side of Gunong Selabor, Semabang entrance to Lobang Batu Cave: UF36183 (not seen). Paratypes. Borneo, Sarawak, First Division, western side of Gunong Selabor, Semabang entrance to Lobang Batu Cave: UF 36184, UF 36185 (not seen).

Other materials

Gunong Silabur, Serian, Sarawak, Malaysia (00°57.45'N, 110°30.20'E): MZU/MOL 17.09, MZU/MOL 17.10, MZU/MOL 17.11, MZU/MOL 17.12, MZU/MOL 17.13, MZU/MOL 17.14, MZU/MOL 17.15, MZU/MOL 17.16, MZU/MOL 17.17, MZU/MOL 17.18, MZU/MOL 17.19, MZU/MOL 17.20, MZU/MOL 17.21, MZU/MOL 17.22, MZU/MOL 17.23, MZU/MOL 17.24.

Description

Protoconch. Color: red to brown. Sculpture pattern: smooth to meshed, with ellipsoid mesh shape. Mesh width: 11–26 µm. Teleoconch. Color: brown to red. First whorl: shouldered, slightly curved above the shoulder, flat, cylindrical below the shoulder. Subsequent whorls: initially shouldered, but soon grading into uniformly rounded and quickly expanding whorls, with a deeply impressed suture; number of whorls: 2 ¼-2 ½. SH: 1.16–1.31 mm, SW: 1.12–1.20 mm, SI: 1.03–1.09. Shell sculpture. Radial sculpture: absent, only weak to strong growth lines are visible. Spiral sculpture: present, strong spiral sculpture. Scales: a single series of low, small and acute, unevenly spaced scales above the periphery, occasionally, in the vicinity of the aperture, subordinate series of minute scales accompany the major series. Aperture. Shape: rounded, tilted below the palatal side. Basal side: rounded, strongly angular at the columellar region. Parietal side: straight, palatal edge attached to the body whorl. AH: 0.58–0.63 mm, AW: 0.75–0.85 mm, AI: 0.73–0.81.

Figure 15. 

Georissa pyrrhoderma Thompson & Dance, 1983. A–C MZU/MOL 17.10 D–K MZU/MOL 17.09. A, D Shell apertural view B Shell side view C Shell rear view E–F Shell cross-section from 3D model G–H Operculum frontal and ventral view I Shell top view J Protoconch side view K Close up of protoconch from top at 1000× magnification. Scale bars: 500 µm (A–I); 200 µm (J); 10 µm (K).

Cross diagnosis

Georissa pyrrhoderma has a shell habitus that is similar to G. kobelti, G. hosei, and G. sepulutensis. The latter two species are high variable and are morphologically, especially in sculpture, closely related to G. pyrrhoderma. Therefore, G. pyrrhoderma is nearly indistinguishable from certain forms of these other species.

Distribution

Only known from the type locality, Gunung Silabur, Serian, Sarawak, Malaysia.

Molecular analysis

In the ML and Bayesian analyses, all G. pyrrhoderma (16S: n = 28; CO1: n = 26) individuals group together in one clade with 99% BS and 100% PP. Its sister clade is G. scalinella + G. kinabatanganensis.

Discussion

In the original description, Thompson and Dance (1983) did not compare G. pyrrhoderma with members of their hosei-group (which our molecular analyses show it belongs in). Instead, they considered it allied to G. borneensis. Possibly this misalignment was caused by the fact that the type specimens appear to lack the series of scales that is present on most of the specimens we collected. Nonetheless, given the restricted range of collection localities at Gunung Silabur and the degree of variability in our material, we consider our and Thompson and Dance’s material as conspecific. The paratypes specimen NHMUK 1984005 (Semabang entrance to Lobang Batu Cave, W. side of Gunong Selabor, 1st. Div., Sarawak, Malaysia: seen) is G. silaburensis.

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.

Figure 16. 

Georissa kinabatanganensis sp. n. A–C Holotype: BOR/MOL 13921 D–K Paratypes: MZU/MOL 17.26. A, D Shell apertural view B Shell side view C Shell rear view E–F Shell cross-section from 3D model G–H Operculum frontal and ventral view I Shell top view J Protoconch side view K Close up of protoconch from top at 1000× magnification. Scale bars: 500 µm (A–I); 200 µm (J); 10 µm (K).

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.

Georissa sepulutensis sp. n.

Georissa scalinella van Benthem-Jutting: Schilthuizen et al. 2005: 134-135 (nonG. scalinella van Benthem-Jutting, 1966).

Type locality

Sepulut valley, Gua Pungiton near Kg. Labang, Sabah, Malaysia (04°42.41'N, 116°36.04'E).

Type material

Holotype. Sepulut valley, Gua Pungiton near Kg. Labang, Sabah, Malaysia (04°42.41'N, 116°36.04'E); BOR/MOL 13922 (leg. M Schilthuizen). Paratypes. Simbaluyon limestone hill, Sabah: RMNH/MOL 333905 (18), RMNH/MOL 333982 (23), RMNH/MOL 334006 (7). Tinahas, Sabah: RMNH/MOL 333984 (>50), RMNH/MOL 334013 (>50). Sepulut valley, Gua Sanaron, Sabah (04°42.05'N, 116°36.01'E): BOR/MOL 36, BOR/MOL 39, BOR/MOL 13870 (1). Sepulut Valley, Gua Pungiton, Sabah (04°42.41'N, 116°36.04'E): BOR/MOL 12278. Sepulut valley, Batu Punggul, Sabah: RMNH/MOL 187650, BOR/MOL.40. Baturong, Sabah: BOR/MOL 37.

Etymology

Named after the town of Sepulut, Sabah, Malaysia, near which the type locality Gua Pungiton, as well as the other known localities, is located.

Description

Protoconch. Color: red to brown. Sculpture: smooth to meshed – semi-oval mesh to undefined mesh pattern. Mesh width: 7–17 µm. Teleoconch. Color: red. First whorl: flat to rounded at the shoulder. Body whorl: rounded, with number of whorls: 2–2 ¾. SH: 1.11–1.52 mm, SW: 1.11–1.37 mm, SI: 0.94–1.07. Shell sculpture. Radial sculpture: absent, only weak growth lines are visible. Spiral sculpture: present, and strongly sculpted. Scales: a series of pointed vertical scales, acute and highly projected, and regularly spaced. Aperture. Shape: oval and tilted below. Basal side: rounded, angular at the columellar region. Parietal side: straight, palatal edge attached to the body whorl. AH: 0.62–0.81 mm, AW: 0.76–0.96 mm, AI: 0.72–0.87. Holotype dimension. SH: 1.34 mm, SW: 1.23 mm, AH: 0.65 mm, AW: 0.82 mm.

Figure 17. 

Georissa sepulutensis sp. n. A–C Holotype: BOR/MOL 13922 D–K Paratypes: BOR/MOL 12278. A, D Shell apertural view B Shell side view C Shell rear view E–F Shell cross-section from 3D model G–H Operculum frontal and ventral view I Shell top view J Protoconch side view K Close up of protoconch from top at 1000× magnification. Scale bars: 500 µm (A–I); 200 µm (J); 10 µm (K).

Cross diagnosis

Unlike Georissa kinabatanganensis, G. sepulutensis has a series of scales only at the shoulder, which makes it resemble in habitus and scale characters G. pyrrhoderma from Gunung Silabur, Sarawak.

Distribution

Distributed in the Sepulut Valley, Sabah; known from the following limestone localities: Simbaluyon, Sanaron, Tinahas, and Pungiton.

Molecular analysis

ML and Bayesian analyses show G. sepulutensis (16S: n = 10; CO1: n = 2) as two clades with 93% BS and 97% PP, and as the sister species to G. kinabatanganensis sp. n.

Discussion

Georissa sepulutensis and G. kinabatanganensis were previously included in G. scalinella (van Benthem-Jutting, 1966). Based on the genetic and morphological distinctness, we here consider them as separate species.

Acknowledgments

The authors thank Sarawak Forest Department (SFD) Sarawak and Economic Planning Unit (EPU), Prime Minister Office, Malaysia, and Sabah Biodiversity Centre for the fieldwork permits NCCD.907.4.4(JLD12)-155 (from SFD), UPE40/200/19/3282 (from EPU), export permit: 15982 (from SFD), and access licenses JKM/MBS.1000-2/2 JLD.5 (28), JKM/MBS.1000-2/2 JLD.3 (167), JKM/MBS.1000-2/2 (167), and JKM/MBS.1000-2/2 (121) (SaBC). Thank you to Grand Perfect Pusaka Sdn. Bhd., Siti Khadijah Reduan, Kirollina Kisun, the heads of villages and local field guides from each of the visited places who helped during the fieldworks. We also thank staff from Naturalis Biodiversity Center, Universiti Malaysia Sarawak, Universiti Malaysia Sabah, and Natural History Museum London, for all the assistance. This study was funded by KNAW Ecologie Fond (J1610/Eco/G437) and Treub Foundation. The first author thanks Ministry of Higher Education Malaysia for the PhD scholarship award at Naturalis Biodiversity Centre and University of Leiden, The Netherlands.

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