''Thylamys pulchellus'', known as the Dry Chaco fat-tailed opossum, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

opossum Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 126 species in 18 genera. Opossums originated in South America and entered North A ...

in the subfamily Didelphinae. The species is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to the

Argentine Argentines, Argentinians or Argentineans are people from Argentina. This connection may be residential, legal, historical, or cultural. For most Argentines, several (or all) of these connections exist and are collectively the source of their ...

portion of

Gran Chaco The Gran Chaco or simply Chaco is a sparsely populated, hot and semiarid lowland tropical dry broadleaf forest natural region of the Río de la Plata basin, divided among eastern Bolivia, western Paraguay, northern Argentina, and a portion o ...

. The species was also once considered to be a part of the common fat-tailed mouse opossum (''Thylamys pusillus'') but is now considered a different species based on morphological and genetic differences.

References

Opossums Marsupials of Argentina Endemic fauna of Argentina Mammals described in 1934 {{marsupial-stub