REVISION OF THE AUSTRAL GENUS METACORNEOLABIUM AND STUDIES IN THE SYSTEMATICS AND BIOGEOGRAPHY OF OMALIINE STAPHYLINIDAE (COLEOPTERA) (NEW ZEALAND, AUSTRALIA, SOUTH AMERICA, BIOGEOGRAPHY)

The beetle subfamily Omaliinae is part of a monophyletic group basal within Staphylinidae sensu lato. Relationships within this group are reviewed, drawing on original and published work. Despite intensive search, no adult synapomorphies are known for Omaliinae; at least some of its tribes are monophyletic. Hypothesized larval synapomorphies support monophyly of a group much like traditional Omaliinae, but larvae of many genera are unknown. Relationships among the tribes are uncertain and placement of some genera remains unclear. Corneolabiini and Microsilphinae are two uncertainly placed subtaxa.;Microsilpha (=Micragyrtes, =Acruliodema, NEW SYNONYMIES) shares Metacorneolabium's range and occurs in southern and western Australia. It includes at least 26 species, each a landmass endemic, only 4 of them already described. Most live in moist temperate forest, a few in drier woodland, but their biology is unknown; structural features suggest hypogeous habits. Collection records are given for all known specimens, but species descriptions are not included.;Cladistic analysis of Metacorneolabium suggests that the New Zealand species form a monophyletic group, sister group of the complexly related Australian + South American species. Explanatory models for austral disjunct distributions are compared; the patterns of area relationships they predict conflict to some extent, allowing some comparative testing. Some pattern replication is found among Metacorneolabium and other austral disjunct groups. It is proposed that Metacorneolabium arose in or near proto-New Zealand Gondwanaland, the basal split in the genus being a result of vicariance or of a single dispersal to Antarctica-South America-Australia as New Zealand split away. Speciation also took place on the remaining land mass and separately on South America and Australia. Metacorneolabium does not support the hypothesis of a Pacifica continent contributing to New Zealand or western South America.;The omaliine genus Metacorneolabium (=Metomalium, NEW SYNONYMY) is revised and its relationships within Corneolabiini and the omaliine group are discussed. Its 22 species (20 of them new) live in temperate forests in New Zealand, southeastern Australia, and southern South America; each species is endemic to one landmass, with much sympatry in each. They seem to be predators living under bark of rotting logs.