The 11 species comprising the fauna of Mecyclothorax Sharp of Papua New Guinea are reviewed, with five species newly described: M. amingwiwae Liebherr, new species,M. andersoni Liebherr, new species,M. brispex Liebherr, new species,M. gressitti Liebherr, new species, and M. medioconstrictus Liebherr, new species. Assessment of characters of the male genitalia and female reproductive tract demonstrate that the fauna is phylogenetically diverse, pointing to prolonged residence in New Guinea by the constituent members of this fauna. All species occupy montane habitats and are characterized by brachyptery, and the assemblage in aggregate exhibits rather low levels of sympatry. This pattern is compared to geographic patterns presented by the similarly brachypterous, but highly diverse and intensively sympatric faunas of the Society and Hawaiian Islands.