More than just a dot: the enigmatic ‘large’ Punctidae of Lord Howe Island (Gastropoda: Stylommatophora)

Punctidae are a family of mostly minute, poorly known land snails with a nearly worldwide distribution. Studies of Australian species are primarily shell-based. We herein revise one of two punctid radiations found on Lord Howe Island located in the Tasman Sea, which encompasses Australia’s largest punctid species. We comprehensively revise the taxonomy of this group, which encompasses three nominal genera, Dignamoconcha, Pernastela, and Charopella, using comparative morpho-anatomy and phylogenetic analyses of mitochondrial (COI, 16S) and nuclear (ITS2, ELAVI8) DNA revealing it to form a single radiation. We treat Pernastela and Charopella as junior synonyms of Dignamoconcha, demonstrate that ‘Pernastela’ gnoma is not a member of this radiation, and synonymize the species Pernastela howensis with Dignamoconcha charon and Charopella zela with Dignamoconcha wilkinsoni, respectively. Dignamoconcha as newly delimited contains three accepted species: D. dulcissima, D. charon, and D. wilkinsoni. In addition, our study shows that Scelidoropa is not a member of Cystopeltidae as previously thought, but is sister to (Charopidae + Punctidae). However, other species formerly assigned to Charopidae are found to be cystopeltids. Radular morphology has utility in identifying higher level groups, such as Punctidae and Scelidoropa, but cannot be used to distinguish between the Cystopeltidae and the Charopidae.