Marmosa murina (Linnaeus, 1758)

PATTON, JAMES L., DA SILVA, MARIA NAZARETH F. & MALCOLM, JAY R., 2000, Mammals Of The Rio Juruá And The Evolutionary And Ecological Diversification Of Amazonia, Bulletin of the American Museum of Natural History 2000 (244), pp. 1-306 : 49-51

Marmosa murina (Linnaeus, 1758)

TYPE LOCALITY: ‘‘Asia, America’’; restrict­ ed to Surinam by Thomas (1911).

DESCRIPTION: A broadly distributed species, this small­bodied murine opossum is medium chestnut brown above and yellowish buff below. The pale hairs of the venter are restricted to the midline, and bordered by broad lateral bands of gray­based fur (fig. 41, right). The tail has large, diamond­shaped scales arranged in bands around the tail. Tail hairs are very small, nonpigmented and less than the length of a single scale. The skull has distinctly flared supraorbital ledges, with a sharp­pointed post­orbital process especially developed in older individuals. The auditory bullae have a uniquely globular alisphenoid portion without separate anterior struts (the bullar types found in the five long­tailed murine opossum genera that Tate [1933] included within his concept of the genus Marmosa [ Thylamys , Gracilinanus , Marmosops , Marmosa , and Micoureus ] are illustrated in Reig et al., 1987).

COMPARISONS: This species of murine opossum is readily distinguished from sympatric Micoureus demerarae and M. regina by its smaller size, lack of dense, woolly pelage, and more gracile skull. Both genera have supraorbital processes, although these are distinctly better developed in Micoureus , and both possess a rounded alisphenoid portion of the bullae lacking anterior struts. Marmosa murina can be confused with same­sized and likely sympatric species of Marmosops , but can be distinguished by a combination of both external and cranial details. For example, in ventral coloration, particularly with regard to the band of graybased hairs lateral to the pale medial portion the specimens of M. murina are quite similar to Marmosops impavidus and Marmosops neblina (see below). The coloration of M murina from the Rio Juruá is similar to that of M. noctivagus , but the former is more chestnut, less gray­brown in color, and the fur of the venter is yellowish­buff as opposed to having nearly white hairs. Marmosa murina also differs from all species of Marmosops in having prominent supraorbital ledges on the skull and in lacking anterior buttressing on the alisphenoid portion of the bullae. Finally, Marmosa murina can be distinguished from Marmosops by its large di­

amond­shaped tail scales arranged in bands, rather than small scales arranged spirally around the tail, with very small and nonpigmented hairs less than the length of a single scale. In Marmosops , the medial hair of each scale triplet is enlarged, petiolate, and is visually black in color, especially in live or fluid preserved individuals.

DISTRIBUTION AND HABITAT: The species was recorded only in the Lower Central and Mouth regions along the river, where it was taken in traps placed on the ground in terra firme forest, or at the interface between terra firme and local igapó forest. Since it is found throughout eastern and southeastern lowland Perú (Voss and Emmons, 1996) and eastern Bolivia (Anderson, 1997), however, M. murina is likely to be found along the entire Rio Jurua´.

REPRODUCTION: Two specimens were parous females of age class 5 (based on Gardner’s [1982] scheme for Didelphis ), one each caught in October and May. Neither had attached young nor showed overt signs of lactation.

COMMENTS: This species is present at all thoroughly worked sites within Amazonia, including eastern and southern Peru´, central and eastern Brazil, and the Guianan lowlands (local faunal reports in Voss and Emmons, 1996). We obtained only three specimens in over 49,000 total trap nights (table 2). Similar capture rates were found during longterm studies in southeastern Perú (Woodman et al., 1991, 1995) and north of Manaus in the central Amazon (Malcolm, 1991a, b), and the species has been taken at only one site within the very large and moderately thoroughly sampled Manu Biosphere Reserve (Pacheco et al., 1993). These few published studies thus suggest that M. murina is either generally rare within Amazonia, or does not readily go to traps. Pine (1973), however, recorded the species as ‘‘common’’ in eastern Amazonia, but did not record trap records or effort, and Louise H. Emmons (personal commun.) found it to be quite common, even if patchily distributed, in secondary areas (as along roadside brush) in the Manu Biosphere in Peru´.

SPECIMENS EXAMINED (n = 3): (9) 1m — JUR 202; (12) 1f — MNFS 746; (13) 1f — JUR 450.