Systematic revision of the snorkel snail genus Rhiostoma Benson, 1860 (Gastropoda, Caenogastropoda, Cyclophoridae) with descriptions of new species

By

Tongkerd, Piyoros
Tumpeesuwan, Sakboworn
Inkhavilay, Khamla
Prasankok, Pongpun
Jeratthitikul, Ekgachai
Somsak Panhā‏
Čhirasak Sutčharit

Type

Article

Date of Publication

2023

Original Publication

ZooKeys

Volume

1142

Pages

1--144

Subjects

DNA barcoding , endemic , Indochina , limestones , operculum , Prosobranchia , taxonomy

Contributed by

Pensoft Publishers

Language

English

Published by

Sofia, Bulgaria Pensoft Publishers

Identifiers

DOI: https://doi.org/10.3897/zookeys.1142.90097

 

Abstract

The snorkel snail genus Rhiostoma Benson, 1860 is comprised of terrestrial cyclophorid snails with wide-ranging species diversity and radiation in Southeast Asia. The typical characters of the genus are a depressed shell, a detached and descending portion of the last whorl with a distinctive peristomal breathing device attached, and a calcareous cup-shaped operculum. Herein, we have revised the systematics of extant species based on shell morphology combined with COI barcoding. From these thirty recognised species, twelve are described as new to science: R. ? amarapuraensesp. nov., R. anceyisp. nov., R. breviocollarsp. nov., R. ebenozosterasp. nov., R. cheliopegmasp. nov., R. furfurosumsp. nov., R. gnomus, sp. nov., R. lannaensesp. nov., R. laoensesp. nov., R. platymorphasp. nov., R. rhothonotaphrosasp. nov., and R. tigrinasp. nov. All conchological characters are provided via illustrations of type specimens and living snails, and descriptions of the shells and radulae. Phylogenetic analysis based on partial COI gene sequences strongly supports the designated morphospecies and a monophyletic Rhiostoma, confirming that all pterocyclinid snails with a calcareous, cup-shaped operculum belong to the same clade. A high intra-specific divergence was observed in R. jalorensis and R. housei populations from locations in close proximity, suggesting a lower dispersal and higher level of isolation. The low inter-specific divergence found in R. hainesi, R. samuiense, R. asiphon, and R. rhothonotaphrosasp. nov. supports their recent diversification and local adaptation, and is congruent with their marked morphological differences. Finally, nine formerly Rhiostoma-placed species were reclassified into either the genus Cyclotus or the genus Opisthoporus.