There are 7 species in 2 genera. All members of the subfamily are very small, ranging from Giles' Planigale at just over 10 grams to the smallest marsupial of all, the 4.3 gram Long-tailed Planigale. Most are about 8 grams, or about half the size of an average mouse. (Planigale novaeguineae or the Papuan Planigale may be an eighth species, or may be better regarded as a subspecies of P. maculata.)
Of the 7 species, two are from the tropical northern part of the continent, the other five from the arid or semi-arid centre. Three of the four planigales have been known for many years—John Gould described the Common Planigale in 1851—but Giles' Planigale and all three ninguais were unknown to science until the 1970s and 1980s.
All 7 species are nocturnal carnivores which hunt a range of small creatures, typically insects, larvae, insect eggs, small lizards and the young of small mammals. Although tiny, they are very bold, at least some of the species regularly take prey larger than themselves. Even the widespread Common Planigale, which can be found in the outer suburbs of Brisbane is poorly known. Until the improvements in biochemical analysis methods towards the end of the 20th century, very little was known about the relationships between the smaller carnivorous marsupials: it is only in recent years that it has been possible to discover that the Planigalinae are a distinct group within the Dasyuromorphia.