The Paraguayan fat-tailed mouse opossum (''Thylamys macrurus'') is a species of

opossum Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 93 species in 18 genera. Opossums originated in South America and entered North ...

in the family Didelphidae. It is found in forested areas of

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

and

Paraguay Paraguay (; ), officially the Republic of Paraguay ( es, República del Paraguay, links=no; gn, Tavakuairetã Paraguái, links=si), is a landlocked country in South America. It is bordered by Argentina to the south and southwest, Brazil to th ...

. It is known only from a few specimens. For two listed specimens, one had a head-and-body length of about 135 mm and a tail length of about 140 mm, while the other had a head-and-body length of about 120 mm and a tail length of about 155 mm. Most of its

fur Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily guard hair on top and thick underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an insulating blanket t ...

is gray, but the shoulder areas are reddish gray, and the

ventral Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Th ...

is pure white or creamy white. There is also a ring of black fur surrounding each

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

. The

surface of the tail is white. The

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal co ...

surface of the tail is gray for the first one third to one half of its length (going from the base to the tip); the remainder of the

surface of the tail is white. The tail is hairless except for about its first ten mm (going from the base to the tip). Although the genus

Thylamys ''Thylamys'' is a genus of opossums in the family Didelphidae. The premaxillae are rounded rather than pointed. The females lack a pouch. The females' nipples are arranged in two symmetrical rows on the abdomen. All species but ''T. macrurus'' ...

is characterized by fat storage in the tail, there is no evidence that this species stores fat in its tail.

References

Opossums Marsupials of South America Mammals of Brazil Mammals of Paraguay Near threatened animals Near threatened biota of South America Mammals described in 1818 Taxa named by Ignaz von Olfers Taxonomy articles created by Polbot {{marsupial-stub