Molecular phylogeny of the land snail family Euconulidae in Thailand and its position in the superfamily Trochomorphoidea (Stylommatophora: Limacoidei), with description of a new genus.

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]