8. Simons’s Mouse Opossum Marmosa simonsi French: Opossum de Simons / German: Simons Zwergbeutelratte / Spanish: Marmosa de Simons Taxonomy. Marmosa simons: Thomas, 1899, “ Puna,” Puna Island, Guayas, Ecuador. Formerly considered a subspecies of M. robinsoni. Monotypic. Distribution. W Ecuador (including Puna I) and NW Peru. Descriptive notes. Head-body 10-7-15:6 cm (males) and 9.8-14.5 cm (females), tail 14-18.9 cm (males) and 12:1-17 cm (females); weight 24-49 g. Simons’s Mouse Opossum has grayish dorsal fur that extends onto head, except for mid-rostral fur, which is paler and contrasts sharply with fur on top of head. There is no mid-rostral stripe. Black eyes are surrounded by dark brown or blackish eye-rings that often reach base of ears, where they fade; cheeks are gray. Tail length is ¢.121% of head-body length, and tail has fur on proximal 10% ofits length. Naked part oftail is mostly brownish dorsally and slightly paler ventrally, contrasting with whitish one-third or one-half of tail’s length. Ventral fur is yellowish, with gray-based hairs along chest and abdominal region and on inner parts of forelimbs and hindlimbs, and with yellowish-buff fur on chin or as a narrow stripe from chin to upper chest. Throat gland is present. Feet are whitish or yellowish-buff, and carpal tubercles are present on males. Female Simons’s Mouse Opossums lack a pouch; number of mammae is unknown. Its karyotype is unknown. Habitat. Mangroves or dry (deciduous) forests between sea level and elevations of 1600 m. A wide range of terrestrial habitats, including lowland and montane moist forests, dry forests, and mangroves, occur throughout the distribution of Simons’s Mouse Opossum, but most specimens have been collected from mangroves or dry (deciduous) forests. Food and Feeding. There is no information available for this species. Breeding. There is no information available for this species. Activity patterns. There is no information available for this species. Movements, Home range and Social organization. There is no information available for this species. Status and Conservation. Simons’s Mouse Opossum has not yet been assessed as a distinct species on The IUCN Red List. At the time of the last [IUCN assessment, Simons’s Mouse Opossum was included as a form of Robinson’s Mouse Opossum (Marmosa robinsoni) but was not named or formally assessed as a subspecies. Conservation status of all opossumsis being reassessed by the IUCN New World Marsupial Specialists Group. Bibliography. Gutiérrez et al. (2010), Rossi (2005), Rossi, Voss & Lunde (2010), Voss et al. (2014).

Published as part of Astúa, D., 2015, Didelphidae, pp. 129-186 in Handbook of the Mammals of the World – Volume 5 Monotremes and Marsupials, Barcelona :Lynx Edicions on page 137, DOI: 10.5281/zenodo.6685333