The black four-eyed opossum (''Philander nigratus'') 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 ...

from

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

Taxonomy

This species was originally described as a

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

of the gray four-eyed opossum under the name ''Metachirus opossum nigratus''. The Spanish

zoologist Zoology ( , ) is the scientific study of animals. Its studies include the structure, embryology, classification, habits, and distribution of all animals, both living and extinct, and how they interact with their ecosystems. Zoology is one ...

Ángel Cabrera Ángel Leopoldo Cabrera (; born 12 September 1969) is an Argentine professional golfer who has played on both the European Tour and PGA Tour. He is known affectionately as ''"El Pato"'' in Spanish ''("The Duck")'' for his waddling gait. He is a ...

went on to synonymize it with the gray four-eyed opossum. The American zoologist Alfred Gardner and later the American mammalogist

Philip Hershkovitz Philip Hershkovitz (12 October 1909 – 15 February 1997) was an American mammalogy, mammalogist. Born in Pittsburgh, he attended the Universities of Pittsburgh and Michigan and lived in South America collecting mammals. In 1947, he was appointed ...

would synonymize this species with Anderson's four-eyed opossum. It was recognized as a distinct species in 2020 following a study of the analysis of the

cytochrome b Cytochrome b is a protein found in the membranes of aerobic cells. In eukaryotic mitochondria (inner membrane) and in aerobic prokaryotes, cytochrome b is a component of respiratory chain complex III () — also known as the bc1 complex or ubiq ...

of the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

and other specimens. This analysis determined its closest relatives to be the dark four-eyed opossum and the

northern four-eyed opossum The northern four-eyed opossum (''Philander vossi'') is a species of opossum from Central America. Taxonomy This species was originally described by the American mammalogist Joel Asaph Allen in 1901 under the name ''Metachirus fuscogriseus pall ...

. This species is recognized by the

American Society of Mammalogists The American Society of Mammalogists (ASM) was founded in 1919. Its primary purpose is to encourage the study of mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence ...

, but not by the

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

Description

The back, muzzle, sides, head, and outer part of the legs of this species is greyish-black, and darker towards face and the middle of the back (but not forming a distinct stripe like the one in Anderson's four-eyed opossum). The underside is grayish, with lighter cream colors around the base of the legs and the underside of the jaw. Like all other ''Philander'' species, it has two light cream-colored spots above the eyes, and the ears are a similar color. Most of the tail is gray, darker at the base of the tail, and the final fourth to fifth of the tail is light gray to whitish. The body length ranges from with the tail length ranging from . Three other species are known to occur close to this species's range: Anderson's four-eyed opossum,

McIlhenny's four-eyed opossum McIlhenny's four-eyed opossum (''Philander mcilhennyi'') is a South American species of opossum. Found in Brazil and Peru, it is almost entirely black, except for white spots above each eye. This species is named for John Stauffer "Jack" McIlhen ...

, and the

common four-eyed opossum The common four-eyed opossum (''Philander canus'') is a species of opossum from South America. Taxonomy Although this species was initially described as a valid species, it was considered a subspecies of the gray four-eyed opossum until 2018. Som ...

. This species lacks a dark dorsal stripe, seen in ''P. andersoni'', and is generally darker. ''P. mcilhennyi'' is usually black instead of dark gray as in this species. ''P. canus'' has a uniformly cream-colored underside, while this species has a gray underside. Additionally, this species has less white on its tail (usually around a fourth or fifth of the tail) while those species have at least a third or more of the tail being white; this species also tends to have larger

molars The molars or molar teeth are large, flat tooth, teeth at the back of the mouth. They are more developed in mammal, mammals. They are used primarily to comminution, grind food during mastication, chewing. The name ''molar'' derives from Latin, '' ...

. The original description of ''P. nigratus'' noted that it did have a black dorsal line, but subsequent examinations of the

seemed to disagree with this.

Range

This 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 ...

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

. It is known only from the eastern foothills of the

Andes mountains The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long and wide (widest between 18°S ...

, in the

departments Department may refer to: * Departmentalization, division of a larger organization into parts with specific responsibility Government and military * Department (administrative division), a geographical and administrative division within a country, ...

Ayacucho Ayacucho (, , derived from the words ''aya'' ("death" or "soul") and ''k'uchu'' ("corner") in honour of the battle of Ayacucho), founded in 1540 as San Juan de la Frontera de Huamanga and known simply as Huamanga (Quechua: Wamanga) until 1825, i ...

and Junín. As of 2020, only eight specimens are known, so its known range may expand in the future. No other ''Philander'' species are known to occur sympatrically with this species, but this may change. Another

didelphid 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 ...

with a range that may be similar to this species is ''

Marmosops juninensis The Junin slender opossum (''Marmosops juninensis'') is a species of South American opossum in the family Didelphidae. It is known only from the valley of the Chanchamayu in Peru (a range that includes Junín Region) where it lives in Andean mo ...

''. The type locality is from the town of Utcuyacu in the Junín department.

References

{{Taxonbar, from=Q110195668 Opossums Marsupials of Peru Endemic fauna of Peru Mammals described in 1923 Taxa named by Oldfield Thomas