There are about 15 species in 2 genera. All members of the subfamily are small: the antechinus species vary in size but are mostly about the same as a mouse or a little larger; one of the two phascogales is slightly larger again, and the Red-tailed Phascogale is the giant of the sufamily at an average of 250 grams, or the same size as a typical Black Rat.
The antechinus group has shrunk considerably in recent years: study of the small marsupial carnivores has led to the realisation that many of the species once classified as "antechinuses" are not as closely related as once thought.
For a small mammalian carnivore, the requirements of gross physical form are fairly strict: on first sight there is very little difference between an antechinus and a planigale or a dibbler—and for that matter not much obvious difference between any of these and the shrews of the northern hemisphere, which although quite unrelated, fill the same sort of ecological niches and often behave in very similar ways.
With the development of advanced microbiological analysis methods towards the end of the 20th century, many species previously thought to be members of the genus Antechinus have been reclassified: the former "Sandstone Antechinus" is now the Northern Dibbler, for example, and the desert-dwelling creature first called a "Fat-tailed Marsupial Mouse" in the late 19th century, became the "Red-eared Antechinus"—only for microbiological evidence to show that is is in fact not an antechinus or a mouse, with the result that is now called the Fat-tailed Pseudantechinus.