A new genus of air-breathing marine slugs from South-East Asia (Gastropoda, Pulmonata, Onchidiidae).

As part of an ongoing effort to revise the taxonomy of air-breathing, marine, onchidiid slugs, a new genus, Dayrat & Goulding, , is described from the mangroves of South-East Asia. It includes two new species, Dayrat & Goulding, , and Dayrat & Goulding, , both distributed from the Malacca Strait to the Philippines and Australia. This study is based on extensive field work in South-East Asia, comparative anatomy, and both mitochondrial (COI and 16S) and nuclear (ITS2 and 28S) DNA sequences. The two new species are found in the same habitat (mud surface in mangrove forests) and are externally cryptic but are distinct anatomically. Both species are also strongly supported by DNA sequences. Three cryptic, least-inclusive, reciprocally-monophyletic units within are regarded as subspecies: Dayrat & Goulding, , Dayrat & Goulding, , and Dayrat & Goulding, The present contribution shows again that species delineation is greatly enhanced by considering comparative anatomy and nuclear DNA sequences in addition to mitochondrial DNA sequences, and that thorough taxonomic revisions are the best and most efficient path to accurate biodiversity knowledge.