Metachirus myosuros (Temminck, 1824)

Voss, Robert S., 2022, An Annotated Checklist Of Recent Opossums (Mammalia: Didelphidae), Bulletin of the American Museum of Natural History 2022 (455), pp. 1-77 : 32

Metachirus myosuros (Temminck, 1824)

TYPE MATERIAL: NMW B-2589, the lectotype (designated by Pohle, 1927), consists of the skin and skull of a juvenile female collected at “Ypanema” (= Ipanema: 23.43° S, 47.60° W; 950 m), São Paulo state, Brazil .

SYNONYMS: antioquiae J.A. Allen, 1916; bolivianus J.A. Allen, 1901; colombianus J.A. Allen, 1900; dentaneus Goldman, 1912; imbutus Thomas, 1923; infuscus Thomas, 1923; modestus Thomas, 1923; personatus Miranda-Ribeiro, 1936; phaeurus Thomas, 1901; tschudii J.A. Allen, 1900.

DISTRIBUTION: As currently understood ( Voss et al., 2019), Metachirus myosuros ranges from southern Mexico possibly throughout the humid lowlands of Central America to South America (Mérida and Cruz, 2015: fig. 2); however, there are curiously large gaps with no recorded specimens from some parts of Central America (e.g., the Atlantic lowlands of Costa Rica). In South America, specimens are known from the humid trans-Andean lowlands of western Colombia and western Ecuador and from most of the tropical and subtropical cis-Andean lowlands (except the northeastern quadrant of Amazonia and the Tocantins-Xingu interfluve; see above and below) to Bolivia, eastern Paraguay, and northern Argentina. There are, unfortunately, no maps that adequately illustrate the South American distribution of this species: Gardner and Dagosto’s (2008) map does not distinguish records of M. myosuros from those of M. nudicaudatus , and Voss et al.’s (2019) map only shows collection localities for sequenced specimens.

REMARKS: See Voss et al. (2019) for illustrations, measurements, and morphological comparisons with Metachirus nudicaudatus . Phylogenetic analyses of cytochrome b sequence data suggest the existence of distinct haplogroups of M. myosuros in (1) Central America, (2) northwestern Amazonia, (3) southwestern Amazonia, and (4) the Atlantic Forest of southeastern Brazil ( Voss et al., 2019). However, despite modestly large sequence divergence among these populations (5.3%–7.6%, uncorrected), there appear to be no consistent phenotypic differences among representative specimens. Therefore, whether these haplogroups represent cryptic taxa or merely geographic variation in mtDNA among populations of a single widespread species remains to be determined.