Marmosops neblina Gardner 1990

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 : 56-60

Marmosops neblina Gardner 1990

TYPE LOCALITY: ‘‘Camp VII (00°50'40''N, 65°58'10''W), 1800 m, Cerro de la Neblina, Territorio Federal Amazonas, Venezuela.’’

DESCRIPTION: This is a medium­sized, dark brown mouse opossum. The single adult male weighed 44 grams with a total length of 299 mm, the condylo­incisive length of the skull 34.5 mm, maxillary toothrow 13.7 mm, and molar toothrow 6.7 mm (table 8). The dorsum is a uniform Mummy Brown (Ridgway, 1912) in color from forehead to furred base of tail. The tail is uniformly and darkly colored to its tip. The whitish ventral hair covers the throat and upper chest, but is restricted to the midline through the abdominal and inguinal regions by broad lateral bands of gray­based, silver­tipped fur (fig. 41, second and third from right). The whitish portion in the abdominal region is less than 1 cm wide. The skull is delicate, with a relatively smooth interorbital region, with beading only weakly developed even in old adults (fig. 46); the palate has both enlarged anterior and posterior vacuities (fig. 45); the mastoid processes are small; and the paroccipital processes are distinctly enlarged. The upper canine is relatively stout, with the width at its base averaging 61% of its length in unworn specimens. Our specimens match those of the type series of M. neblina , as detailed by Gardner (1989) in his original description in external color and color pattern, particularly in the narrow mid­ventral white stripe bordered laterally by broad areas of darker pelage with pale­tipped hairs. Our specimens also possess the markedly developed accessory cusps between the paracone and metacone on the third upper molars and, therefore, the shallowly concave labial outline detailed in Gardner’s diagnosis (1989: 414).

COMPARISONS: This species can be distinguished from M. noctivagus and M. parvidens in the same way as can M. impavidus with the exception that the interorbital region of M. neblina is even smoother with weaker supraorbital beading. For differences between M. neblina and M. impavidus , see the section above for M. impavidus .

COMMENTS: As suggested in the analyses presented by Mustrangi and Patton (1997) we recognize N. neblina as a species separate from M. impavidus . With available samples

although the two species are apparently close phyletic relatives (fig. 43), they are sympatric at two localities and are readily separable by the morphological characters listed above.

DISTRIBUTION AND HABITAT: This taxon is known from a few localities in the Headwaters, Upper, and Lower Central regions of the Rio Jurua´, all from várzea forest or disturbed river­edge areas. Two specimens were taken at approximately 1.5 m; the remainder were taken in traps placed on the ground. Single specimens of both M. neblina and M. impavidus were obtained at Igarapé Porongaba (locality 1) and Altamira (locality 9), where they were segregated by habitat in both cases.

REPRODUCTION: Specimens were collected in both wet and dry seasons. These include mostly juvenile or subadult individuals (with an incompletely erupted molar series), sug­ gesting that breeding occurs throughout the year. The single adult female (Nova Empresa, locality 8) showed no signs of recent past breeding activity.

KARYOTYPE: 2n = 14, FN = 24 (fig. 47B) Chromosomal data are available from two individuals (JLP 15215, from locality h; and MNFS 703, locality 11). The karyotype appears identical to that described above for M. impavidus .

SPECIMENS EXAMINED (n = 11): (1) 1f — MNFS 1067; (c) 1m — MNFS 994; (3) 2 m — MNFS 1637, JUR 210; (8) 1m — JLP 15450; (h) 1f — JLP 15215; (9) 1f — JLP 16052; (10) 1m — MNFS 943; (11) 1m, 2 f — MNFS 703, 718–719.

Marmosops noctivagus (Tschudi, 1844)

TYPE LOCALITY: ‘‘Der mittleren und tiefen

Waldregion’’; restricted by Tate (1933) to Montaña de Vitoc, near Chanchamayo, Río Perené drainage, Departamento de Junín, Peru´ .

DESCRIPTION: This is the largest of the four species of Marmosops recorded from the Rio Juruá drainage, averaging 321.1 mm in total length, 37.2 mm in condyloincisive length of the skull, and 54 g in weight (table 8). The dorsal color is paler, more orangish­redbrown than that of either M. neblina or M. parvidens , but similar to that of M. impavidus , ranging from Cinnamon­Brown to Dresden Brown (Ridgway, 1912). The venter is broadly white to cream from chin to inguinal region, either without a lateral band of graybased hairs separating it from the sides and back or, if present, the band is narrow and confined to the abdominal region (fig. 41, left). The skull of noctivagus is large, with well­developed anterior and posterior pairs of palatal vacuities (fig. 45) and well­developed supraorbital beading that forms clearly evident ledges with small postorbital processes in older individuals (fig. 46). The anterior opening of the infraorbital foramen is positioned above the posterior root of PM4 The maxillary toothrow averages 15.7 mm in length, the upper molar series 7.7 mm. The upper canine is relatively short and stout with the width at the base averaging 65.5% of its length.

COMPARISONS: Marmosops noctivagus can be readily distinguished from M. neblina by its larger size, brighter dorsal pelage, pure white venter without a lateral border of graybased hairs (fig. 41), larger molar series and individual teeth, and well­developed supraorbital beading with ledges clearly evident in older individuals (fig. 46); it differs from M. impavidus in the same set of characters, with the exception that the dorsal color of both is quite similar. The large size, supraorbital beading, and presence of posterior palatal vacuities easily distinguish M. noctivagus from M. parvidens .

DISTRIBUTION AND HABITAT: This species was found in all four sampling areas along the Rio Juruá except the Lower Central Region. It was very common at Penedo (locality 7) where 18 specimens were obtained, mostly in terra firme forest but also in second­growth. One specimen was shot at a height of about 10 m, two were shot at heights of about 2 m, with all others either trapped or shot while on the ground. Specimens from the Headwaters Region came from both terra firme and várzea forest (lo­ calities 1 versus 2 and 3); all those from the Upper Central or Mouth regions were taken in terra firme communities.

REPRODUCTION: We found no females with attached young. Specimens taken at localities in the Headwaters Region were collected in the rainy season and were all either juveniles or nulliparous adult females. Only one of the 11 adults (M1–M4 fully erupted) collected at Penedo (locality 7) during the height of the dry season in August showed evidence of prior suckling in the form of the discolored orange inguinal region and evident nipples.

KARYOTYPE: 2n = 14, FN = 24 (fig. 47C) Karyotypic data are available from four individuals (MNFS 369, 381, JLP 15566, 15676). The autosomal complement consists of four pairs of large meta­ and submetacentric and two pairs of small metacentric ele­

ments; X­chromosome is a small metacentric, and the Y is an even smaller metacentric. This karyotype appears to differ from that of M. impavidus and M. neblina by two, versus one, small pairs of metacentric autosomes. Specimens from the Rio Juruá have the same karyotype as do those from eastern Perú (Reig et al., 1977) and Bolivia (Palma and Yates, 1996).

SPECIMENS EXAMINED (n = 40): (1) 3m, 1f — MNFS 1065, 1066, 1384, 1403; (2) 1f — MNFS 1184; (3) 4m — MNFS 1577, 1598, 1674, JUR 226; (6) 3f — JLP 15566, 15601, 15676; (7) 9m, 10f, 1 unknown — MNFS 336, 360–361, 369, 371, 381, 398, 403, 414– 418, 495, 522, JLP 15253, 15306, 15313 15353, 15360; (15) 5m, 3f — JUR 251, 283 315–317, 331, 348, 397.