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Based on several field investigations, many molluscan shells and chondrichthyan teeth, together with other invertebrate and actinopterygian remains were found from the marine Bangkok Clay deposits in Ongkharak, Nakhon Nayok, at a depth of ~ 5–7 m below the topsoil surface. Animal macrofossils recovered from these Holocene marine deposits were identified and their chronological context was investigated in order to reconstruct the paleoenvironments of the area at that time. The majority of marine fossils recovered from the site consist of molluscs, with a total of 63 species identified. Other invertebrate species include a stony coral, a mud lobster, barnacles, and a sea urchin. The vertebrates are represented by fish remains, including carcharhinid shark teeth from at least nine species, stingray and trichiurid teeth, and one sciaenid otolith. The molluscan fauna indicates that the paleoenvironments of the area corresponded to intertidal to sublittoral zones, where some areas were mangrove forests and intertidal mudflats. The fish fauna is dominated by the river shark Glyphis, indicating freshwater influences and possibly occasional brackish conditions. The carbon-14 analysis of mollusc and charcoal remains shows that deposition of the marine sediment sequence began during the mid-Holocene, spanning approximately from 8,800 to 5,300 cal yr BP. This study provides in-depth insights into the diversity of fishes, marine molluscs, and other invertebrates from the Bangkok Clay deposits, supporting the existence of a marine transgression onto the Lower Central Plain of Thailand during the mid-Holocene. [ABSTRACT FROM AUTHOR]

This paper reassesses the taxonomy and systematics of 11 arboreal snail species in the genus Amphidromus from Vietnam, Cambodia, Indonesia and Laos (A. bozhii Wang, 2019, A. buelowi Fruhstorfer, 1905, A. costifer Smith, 1893, A. haematostoma Möllendorff, 1898, A. ingens Möllendorff, 1900, A. madelineae Thach, 2020, A. metabletus Möllendorff, 1900, A. pankowskianus Thach, 2020, A. placostylus Möllendorff, 1900, A. roseolabiatus Fulton, 1896, and A. thachi Huber, 2015). The taxonomic validity of each species is supported by a phylogenetic analysis of mitochondrial COI and 16S rRNA gene fragments from 17 ingroup taxa. Amphidromus buelowi was found to comprise two populations from two distant localities, one from Mount Singgalang, West Sumatra, Indonesia and the other from southern Vietnam. The samples from southern Vietnam were previously described as A. asper Haas, 1934 and A. franzhuberi Thach, 2016, but they are now treated as junior synonyms of A. buelowi in this study. In addition, two species from Vietnam are described as new to science, viz. A. asperoides Jirapatrasilp & Lee, sp. nov. and A. ingensoides Jirapatrasilp & Lee, sp. nov., each of which is conchologically comparable to A. buelowi and A. ingens, respectively. [ABSTRACT FROM AUTHOR]

The Euconulidae is a globally distributed land snail family but there is no record of this family from Thailand. In this study, we describe a new genus, Siamoconus gen. nov., based on comparative studies of the shell characteristics, external morphology of animals, radula, genital and spermatophore structures, and molecular phylogeny. We performed phylogenetic analyses of two mitochondrial gene fragment (cytochrome c oxidase I, COI; and 16S rRNA) and one nuclear (28S rRNA) gene fragment to clarify the relationships with other euconulid genera and its position in the superfamily Trochomorphoidea. We also analysed shell morphometrics, male genitalia and mantle pigmentation of Siamoconus gen. nov., confirming the status of three new species with keeled shells (S. boreas sp. nov., S. coleus sp. nov. and S. geotrochoides sp. nov.) and one new species with a rounded shell (S. destitutus sp. nov.). These new species are restricted to limestone areas in northern and north-eastern Thailand. We also re-examined the status of other genera in the superfamily Trochomorphoidea based on shell features, body pigmentation, radula, genital anatomy, spermatophore morphology, and a phylogenetic analysis of all available trochomorphoidean DNA sequences. Our analysis suggests that the family Geotrochidae, previously synonymised with the Trochomorphidae, should be resurrected to represent the genus Geotrochus from Borneo, and this family is retrieved as the sister clade of the Dyakiidae. ZooBank: urn:lsid:zoobank.org:pub:C5205F4E-5DDE-42E6-A532-761CAFE099C3 Euconulidae is one of the most diverse families in the superfamily Trochomorphoidea with a distribution that is almost world-wide but there is no record of this family from Thailand. We describe four new species of Siamoconus gen. nov., a new euconulid genus and also perform phylogenetic analyses of one nuclear and two mitochondrial gene fragments to clarify the systematic position of this new genus and the relationships to other genera in the superfamily Trochomorphoidea. In addition, the family Geotrochidae, previously synonymised with the Trochomorphidae, is resurrected as sister clade of the Dyakiidae within the superfamily Trochmorphoidea. [ABSTRACT FROM AUTHOR]

Thirteen hypselostomatid microsnails have been reported so far from Cambodia: 10 species from the Mekong Delta karsts in the south and three species from the Sisophon-Battambang limestone hills in the west. Herein, Gyliotrachela torticollis Benthem Jutting, 1962, the only species previously reported from the Battambang, is redescribed based on near-type locality specimens. We describe a new species, Gyliotrachela khmeriana sp. nov., from the Cambodian Sisophon-Battambang limestone hills. This new species differs from all other known hypselostomatid species in having a short and straight tuba, protoconch sculptures with shallow pits and spiral striations, and apertural dentition with parietal, angular, and four other lamellae on the palatal wall. In addition, specimens of 'Anauchen srakeoensis Panha and Burch, 2004', previously recorded only in Thailand, were collected from limestone hills in Sisophon, redescribed based on shell morphology and taxonomically relocated as a member of the Hypselostoma. [ABSTRACT FROM AUTHOR]

The pill millipede genus Hyperglomeris Silvestri, 1917 is reported from Laos for the first time. Two new species, namely H. bicaudata Likhitrakarn, sp. nov. and H. inkhavilayi Likhitrakarn, sp. nov., from Houaphanh and Khammouane provinces, northern Laos, are described and illustrated based on morphological characters and molecular analyses. Sequences of COI gene were used as DNA barcoding markers, and successfully supported the accurate identification of other Glomeridae species. Interspecific divergence of the COI uncorrected p-distance between these new species and other Hyperglomeris species ranged from 7.84-13.07%, while the intraspecific divergence was 0.45% in H. inkhavilayi sp. nov. and 5.3% in H. bicaudata sp. nov. The updated status of Hyperglomeris, a map of its distribution, and identification keys for all species are given. [ABSTRACT FROM AUTHOR]

Species of colourful arboreal snails of the genus Amphidromus from Southeast Asia commonly exhibit high intraspecific variation in shell morphology. Although highly polymorphic Amphidromus specimens with different colouration have been collected at the same locality and were revealed to possess similar genital organs, there is yet no morphometric or DNA analyses of these different shell morphs. This study is the first to reveal that both striped and stripeless morphs of A. cruentatus from Laos and Vietnam belong to the same mitochondrial (COI and 16S rRNA) lineage. Although the shell colouration between the striped and stripeless morphs is markedly different, morphometric and shell outline-based analyses indicated an overall similarity in shell shape. We also revised the systematics of A. cruentatus, in which we treated similar related species, namely A. eudeli, A. fuscolabris, A. thakhekensis, A. gerberi bolovenensis, A. goldbergi, A. pengzhuoani, A. eichhorsti and A. pankowskiae as junior synonyms of A. cruentatus. Amphidromus daoae, A. anhdaoorum, A. stungtrengensis, A. yangbayensis and A. yenlinhae, which were formerly regarded as junior synonyms, are considered as species different from A. cruentatus based on shell morphology and morphometric analyses. Preliminary phylogenetic analyses also retrieved some Amphidromus species groups as distinct mitochondrial lineages. [ABSTRACT FROM AUTHOR]

Thailand is located at the crossroads of several biogeographical regions, and boasts a high level of biodiversity, especially among the malacofauna. The most recent checklist of land snail species in Thailand was compiled more than twenty years ago, and so this checklist needs revision and the addition of newly discovered taxa. This study updates the taxonomy and species list of the operculated land snail family Pupinidae from Thailand. This snail family is diverse and abundant, and can be found in various natural habitats in Southeast Asia. Although the taxonomy of some Southeast Asian pupinid genera has been reviewed, studies of Pupina Vignard, 1829, which contains the highest number of species, and a lesser-known genus Pupinella Gray, 1850 are still lacking. Herein we present an annotated checklist with an up-to-date systematic framework of the Pupinidae in Thailand based on both field investigations and literature surveys, and include the taxonomic treatment of all Pupina and Pupinella species from mainland Southeast Asia. This annotated checklist contains 30 nominal species and two subspecies from seven genera currently known to occur in Thailand. We describe two species of Pseudopomatias (P. doiangkhangensis Jirapatrasilp, sp. nov. and P. pallgergelyi Jirapatrasilp, sp. nov.), five species and one subspecies of Pupina (P. bensoni Jirapatrasilp, sp. nov., P. bilabiata Jirapatrasilp, sp. nov., P. godwinausteni Jirapatrasilp, sp. nov., P. latisulci Jirapatrasilp, sp. nov., P. stoliczkai Jirapatrasilp, sp. nov., and P. dorri isanensis Jirapatrasilp, ssp. nov.) as new to science. New records of Coptocheilus sumatranus, Pupinella mansuyi, and Rhaphaulus tonkinensis are also reported from Thailand. The mainland Southeast Asian Pupina species are classified into three species groups (Pupina artata group, Pupina arula group, and Pupina aureola group) based on the distinction of shell teeth and canals, and operculum. Three species formerly in Pupina from Vietnam are allocated to Pupinella (P. illustris comb. nov., P. sonlaensis comb. nov., and P. thaitranbaii comb. nov.) due to the presence of a funnel-like anterior canal. [ABSTRACT FROM AUTHOR]