<mods:titleid="EFC7DD7F008993327D1FEA87B86CB6D9">Systematic revision of the snorkel snail genus Rhiostoma Benson, 1860 (Gastropoda, Caenogastropoda, Cyclophoridae) with descriptions of new species</mods:title>
<mods:affiliationid="B39C76B6277DB7BC8AFC3E5CA69A6D36">Animal Systematics Research Unit, Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand</mods:affiliation>
<mods:affiliationid="A8481508F9F666ADCAF04DC3757EC246">Animal Systematics Research Unit, Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand & Present address: Department of Biology, Faculty of Science, Mahasarakham University, Kantharawichai, Maha Sarakham 44150 Thailand</mods:affiliation>
<mods:affiliationid="74C79C65E6F4A51365B1BD24DD61ECB1">Department of Biology, Faculty of Natural Science, National University of Laos, P. O. Box 7322, Dongdok, Vientiane, Laos</mods:affiliation>
<mods:affiliationid="A64C6C7068E6573D8190DC4B03193A9E">School of Biology, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand</mods:affiliation>
<mods:affiliationid="2FBAEC6BBAAB4FF1647C478527302451">Animal Systematics and Molecular Ecology Laboratory, Department of Biology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand</mods:affiliation>
<mods:affiliationid="B0E95ED4B6B3353A96CC227D388FC335">Animal Systematics Research Unit, Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand</mods:affiliation>
<mods:affiliationid="98B93599CBE8758AF4F9071DF9913616">Animal Systematics Research Unit, Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand</mods:affiliation>
<taxonomicNameid="D383307AF1F5AB9F2A7DDD428922514A"ID-CoL="B3CKK"LSID="https://zoobank.org/99F7CC56-90BD-46F2-B082-2EC1650567CC"authority="Tongkerd & Tumpeesuwan"authorityName="Tongkerd & Tumpeesuwan"authorityYear="2023"class="Gastropoda"family="Cyclophoridae"genus="Rhiostoma"higherTaxonomySource="treatment-meta"kingdom="Animalia"lsidName="Rhiostoma cheliopegma"order="Architaenioglossa"pageId="0"pageNumber="1"phylum="Mollusca"rank="species"species="cheliopegma"status="sp. nov.">Rhiostoma cheliopegma Tongkerd & Tumpeesuwan</taxonomicName>
<figureCitationid="9D633FAE4D3E87CA7F177C2A55E510CE"captionStart="Figure 44"captionStartId="F44"captionText="Figure 44. Distribution map of Rhiostoma morleti - species group."figureDoi="10.3897/zookeys.1142.90097.figure44"httpUri="https://binary.pensoft.net/fig/799902"pageId="0"pageNumber="1">Figs 44</figureCitation>
<figureCitationid="8A211661F7FB4192CA498BD9A3D76157"captionStart="Figure 50"captionStartId="F50"captionText="Figure 50. Shell of Rhiostoma cheliopegma sp. nov. A holotype CUMZ 3985 / 1 from Tham Takien, Khao Chamao, Rayong B, C paratypes CUMZ 3985 / 2 from type locality D, E from Tham Khao Loi, Khao Chamao, Rayong D specimen CUMZ 4818 and E specimen CUMZ 4871 F paratype CUMZ 4853 from type locality with albinistic shell form."figureDoi="10.3897/zookeys.1142.90097.figure50"httpUri="https://binary.pensoft.net/fig/799908"pageId="0"pageNumber="1">, 50</figureCitation>
<figureCitationid="5D220185E5435587BE690746096A3E4B"captionStart="Figure 53"captionStartId="F53"captionText="Figure 53. Radula morphology A Rhiostoma cambodjense, specimens CUMZ 4714 from Khao Chakan, Srakeo B Rhiostoma cheliopegma sp. nov., paratype CUMZ CUMZ 3985 / 2 Tham Takien, Khao Chamao, Rayong C Rhiostoma gnomus sp. nov. paratype CUMZ 4717 from Pha Chu, Na Noi, Nan D Rhiostoma laosense sp. nov. specimen CUMZ 10205 from Tad Muang, Khammouane, Laos."figureDoi="10.3897/zookeys.1142.90097.figure53"httpUri="https://binary.pensoft.net/fig/799911"pageId="0"pageNumber="1">, 53B</figureCitation>
<taxonomicNameid="6844919F670E8C6BA8E79A3641DE73BE"authority="Tongkerd & Tumpeesuwan & Inkhavilay & Prasankok & Jeratthitikul & Panha & Sutcharit, 2023"authorityName="Tongkerd & Tumpeesuwan & Inkhavilay & Prasankok & Jeratthitikul & Panha & Sutcharit"authorityYear="2023"class="Gastropoda"family="Cyclophoridae"genus="Rhiostoma"higherTaxonomySource="treatment-meta"kingdom="Animalia"lsidName="Rhiostoma"order="Architaenioglossa"pageId="0"pageNumber="1"phylum="Mollusca"rank="genus"status="sp. nov.">Rhiostoma</taxonomicName>
<bibRefCitationid="A975B0FF7380E1C91A80F1ED964B90B2"author="Tumpeesuwan, S"journalOrPublisher="Master Thesis, Department of Biology, Faculty of Science, Chulalongkorn University"pageId="0"pageNumber="1"refId="B175"refString="Tumpeesuwan, S, 2001. Taxonomy of snorkel snails genus Rhiostoma Benson, 1860 in Thailand. Master Thesis, Department of Biology, Faculty of Science, Chulalongkorn University"title="Taxonomy of snorkel snails genus Rhiostoma Benson, 1860 in Thailand."year="2001">Tumpeesuwan 2001</bibRefCitation>
<figureCitationid="56C65C956FB68297F92264A7B3FFC15D"captionStart="Figure 50"captionStartId="F50"captionText="Figure 50. Shell of Rhiostoma cheliopegma sp. nov. A holotype CUMZ 3985 / 1 from Tham Takien, Khao Chamao, Rayong B, C paratypes CUMZ 3985 / 2 from type locality D, E from Tham Khao Loi, Khao Chamao, Rayong D specimen CUMZ 4818 and E specimen CUMZ 4871 F paratype CUMZ 4853 from type locality with albinistic shell form."figureDoi="10.3897/zookeys.1142.90097.figure50"httpUri="https://binary.pensoft.net/fig/799908"pageId="0"pageNumber="1">50A</figureCitation>
<figureCitationid="C514478F66F91D56A786A888843CEC16"captionStart="Figure 50"captionStartId="F50"captionText="Figure 50. Shell of Rhiostoma cheliopegma sp. nov. A holotype CUMZ 3985 / 1 from Tham Takien, Khao Chamao, Rayong B, C paratypes CUMZ 3985 / 2 from type locality D, E from Tham Khao Loi, Khao Chamao, Rayong D specimen CUMZ 4818 and E specimen CUMZ 4871 F paratype CUMZ 4853 from type locality with albinistic shell form."figureDoi="10.3897/zookeys.1142.90097.figure50"httpUri="https://binary.pensoft.net/fig/799908"pageId="0"pageNumber="1">50B, C</figureCitation>
<figureCitationid="6577BA3705429EF95F81A5F09CA794AB"captionStart="Figure 50"captionStartId="F50"captionText="Figure 50. Shell of Rhiostoma cheliopegma sp. nov. A holotype CUMZ 3985 / 1 from Tham Takien, Khao Chamao, Rayong B, C paratypes CUMZ 3985 / 2 from type locality D, E from Tham Khao Loi, Khao Chamao, Rayong D specimen CUMZ 4818 and E specimen CUMZ 4871 F paratype CUMZ 4853 from type locality with albinistic shell form."figureDoi="10.3897/zookeys.1142.90097.figure50"httpUri="https://binary.pensoft.net/fig/799908"pageId="0"pageNumber="1">50F</figureCitation>
<taxonomicNameid="0E4C0598C08009780EA67E2B2AD0BFCA"authorityName="Tongkerd & Tumpeesuwan"authorityYear="2023"class="Gastropoda"family="Cyclophoridae"genus="Rhiostoma"kingdom="Animalia"lsidName="Rhiostoma cheliopegma"order="Architaenioglossa"pageId="0"pageNumber="1"phylum="Mollusca"rank="species"species="cheliopegma">
<materialsCitationid="6C713980939212112D1D73917385EA46"collectingDate="2023-01-01"collectingDateMax="2023-12-31"collectingDateMin="2023-01-01"country="Thailand"location="Tham Neramit Bureau of Monks"specimenCount="1"stateProvince="Chonburi">
<locationid="5D89BCBF593E4322B82D010375649CBF"LSID="urn:lsid:plazi:treatment:4AD27BA693EF5C3C8227360D6DFFE297:5D89BCBF593E4322B82D010375649CBF"country="Thailand"name="Tham Neramit Bureau of Monks"stateProvince="Chonburi">Tham Neramit Bureau of Monks</location>
<figureCitationid="6E77F9957AE351E3DF411328D215C5A0"captionStart="Figure 50"captionStartId="F50"captionText="Figure 50. Shell of Rhiostoma cheliopegma sp. nov. A holotype CUMZ 3985 / 1 from Tham Takien, Khao Chamao, Rayong B, C paratypes CUMZ 3985 / 2 from type locality D, E from Tham Khao Loi, Khao Chamao, Rayong D specimen CUMZ 4818 and E specimen CUMZ 4871 F paratype CUMZ 4853 from type locality with albinistic shell form."figureDoi="10.3897/zookeys.1142.90097.figure50"httpUri="https://binary.pensoft.net/fig/799908"pageId="0"pageNumber="1">50D</figureCitation>
<figureCitationid="687EF7F7EEA7138AFCAC1B39E7B37644"captionStart="Figure 50"captionStartId="F50"captionText="Figure 50. Shell of Rhiostoma cheliopegma sp. nov. A holotype CUMZ 3985 / 1 from Tham Takien, Khao Chamao, Rayong B, C paratypes CUMZ 3985 / 2 from type locality D, E from Tham Khao Loi, Khao Chamao, Rayong D specimen CUMZ 4818 and E specimen CUMZ 4871 F paratype CUMZ 4853 from type locality with albinistic shell form."figureDoi="10.3897/zookeys.1142.90097.figure50"httpUri="https://binary.pensoft.net/fig/799908"pageId="0"pageNumber="1">50E</figureCitation>
<paragraphid="0073048443959438995BFB45BD23F7A0"pageId="0"pageNumber="1">Shell small, depressed, and without detached whorl. Peristome multi-layered; lip thickened; breathing device notch-shaped. Shell colour usually uniformly reddish to dark brown. Operculum calcareous, thick, tall cup-shaped, and multispiral.</paragraph>
<taxonomicNameid="5181C525D232D61757DC38E13E32297B"authorityName="Tongkerd & Tumpeesuwan"authorityYear="2023"class="Gastropoda"family="Cyclophoridae"genus="Rhiostoma"kingdom="Animalia"lsidName="Rhiostoma cheliopegma"order="Architaenioglossa"pageId="0"pageNumber="1"phylum="Mollusca"rank="species"species="cheliopegma">
by a sub-discoidal shell, a uniform or blotched reddish brown colour pattern, apertural lip thickened, and expanded tall cup-shaped operculum. For comparison,
has a heliciform shell, uniformly brownish or yellowish shell, apertural lip thin, and low cup-shaped operculum. In addition, the COI barcoding in this study suggests separating these two species (Fig.
<figureCitationid="69AB3C2A5544C0D68D8D5C4F2FBB0B87"captionStart="Figure 3"captionStartId="F3"captionText="Figure 3. Maximum likelihood (ML) tree showing the relationships among Rhiostoma species based on 660 bp of the mitochondrial COI gene sequence. The major nodes are indicated by numbers as the Maximum likelihood (ML) bootstrap values and Bayesian posterior probabilities of Bayesian inference (BI), respectively. Nodes with sufficient support by both ML and BI are indicated by black circles, and nodes with partial support by only ML are indicated by grey circles, and only BI by white circles. Newly described species in this study are highlighted in blue."figureDoi="10.3897/zookeys.1142.90097.figure3"httpUri="https://binary.pensoft.net/fig/799861"pageId="0"pageNumber="1">3</figureCitation>
Shell small, width 17.1-20.0 mm, height 5.8-11.5 mm, thickened, and sub-discoidal shape. Apex acute with dark colouration; spire slightly elevated. Whorls 4 to 5, convex, increasing regularly; suture wide and shallow; last whorl rounded. Shell surface nearly smooth with fine growth lines. Periostracum thin, corneous, and transparent. Shell colour usually uniformly reddish to dark brownish (rarely with albinistic forms), sometimes with unclear patterns; with narrow dark brown spiral band on periphery. Detached whorl usually absent. Peristome circular and double; lip thickened, expanded and multi-layered. Aperture opened sub-laterally. Breathing device notch-shaped; outer lip protruding, with narrow groove; inner lip with shallow to deep incision. Umbilicus widely opened and deep. Operculum calcareous, thickened, tall and cup-shaped, and multispiral (Fig.
<figureCitationid="F860F690B2F7E854CD91B2B15CFA684A"captionStart="Figure 50"captionStartId="F50"captionText="Figure 50. Shell of Rhiostoma cheliopegma sp. nov. A holotype CUMZ 3985 / 1 from Tham Takien, Khao Chamao, Rayong B, C paratypes CUMZ 3985 / 2 from type locality D, E from Tham Khao Loi, Khao Chamao, Rayong D specimen CUMZ 4818 and E specimen CUMZ 4871 F paratype CUMZ 4853 from type locality with albinistic shell form."figureDoi="10.3897/zookeys.1142.90097.figure50"httpUri="https://binary.pensoft.net/fig/799908"pageId="0"pageNumber="1">50</figureCitation>
. Central tooth with large central cusp and two lateral cusps on each side. Lateral teeth have four cusps: central cusp large, triangular, and flanked by two small inner cusps and one outer cusp. Marginal teeth each consisting of three pointed cusps (Fig.
<figureCitationid="4A6260CB8D110DBD67A4CA5FC41A5F24"captionStart="Figure 44"captionStartId="F44"captionText="Figure 44. Distribution map of Rhiostoma morleti - species group."figureDoi="10.3897/zookeys.1142.90097.figure44"httpUri="https://binary.pensoft.net/fig/799902"pageId="0"pageNumber="1">44</figureCitation>
<figureCitationid="0C91C26559801361BC0D1E3C7DA77003"captionStart="Figure 3"captionStartId="F3"captionText="Figure 3. Maximum likelihood (ML) tree showing the relationships among Rhiostoma species based on 660 bp of the mitochondrial COI gene sequence. The major nodes are indicated by numbers as the Maximum likelihood (ML) bootstrap values and Bayesian posterior probabilities of Bayesian inference (BI), respectively. Nodes with sufficient support by both ML and BI are indicated by black circles, and nodes with partial support by only ML are indicated by grey circles, and only BI by white circles. Newly described species in this study are highlighted in blue."figureDoi="10.3897/zookeys.1142.90097.figure3"httpUri="https://binary.pensoft.net/fig/799861"pageId="0"pageNumber="1">3</figureCitation>
). We assign them as conspecific due to the indistinguishable shell form and breathing device and their geographical proximity in eastern Thailand. Therefore, more effort should be paid to additional molecular markers, and morphometric analyses are required to determine whether these distinct subclades should be recognised as a distinct taxon.
