The Agile Antechinus is a species of small carnivorous marsupial

Marsupial

Marsupials are an infraclass of mammals, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia, New Guinea, and nearby islands, with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central...

 of the family Dasyuridae

Dasyuridae

Dasyuridae is a family of marsupials native to Australia and New Guinea, including 61 species divided into 15 genera. Many are small and mouse-like, giving them the misnomer marsupial mice, but the group also includes the cat-sized quolls, as well as the Tasmanian Devil...

. It is found in Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

.
The Agile Antechinus was long considered to be a form of the Brown Antechinus

Brown Antechinus

The Brown Antechinus , also known as Stuart's Antechinus and Macleay's Marsupial Mouse, is a species of small carnivorous marsupial of the family Dasyuridae.-Taxonomy:...

 (Antechinus stuartii), and was only recognised as a distinct species after a study of genetic variation

Genetic variation

Genetic variation, variation in alleles of genes, occurs both within and among populations. Genetic variation is important because it provides the “raw material” for natural selection. Genetic variation is brought about by mutation, a change in a chemical structure of a gene. Polyploidy is an...

 within the Brown Antechinus in 1980. However, it was not formally described until 1998.
The Agile Antechinus is nearly indistinguishable from the Brown Antechinus, but it is slightly smaller and its fur has a more greyish tinge.