2004 
the upper canines have small posterior ac- 
cessory cusps. Although one adult male 
(MSB 55843) has an almost-naked patch of 
skin and a streak of red-stained fur on the 
midline of the throat, two others (CBF 7531, 
LHE 1541) have no trace of a gular gland. 
All three adult males have well-developed, 
blade-like lateral carpal tubercles, and the 
scrotum is pale, with white fur and unpig- 
mented skin. None of the females we ex- 
amined had well-developed mammae, so it is 
not known whether or not this taxon has pec- 
toral teats. 
There is noteworthy pelage color variation 
among the material at hand. All of the spec- 
imens we examined from Beni, Cochabamba, 
La Paz, and western Santa Cruz have dull 
reddish-brown dorsal fur, self-whitish ventral 
fur bordered by more-or-less distinct lateral 
zones of gray-based hairs, and unicolored 
tails. By contrast, the single available skin 
from eastern Santa Cruz (LHE 1541)!° has 
pale grayish-brown dorsal fur, self-cream 
ventral fur (without well- defined lateral 
zones of gray-based hairs), and an indistinct- 
ly bicolored tail. Despite these pigmental dif- 
ferences, specimens from eastern Santa Cruz 
do not differ from the rest of our Bolivian 
material in other respects (e.g., measure- 
ments and qualitative craniodental traits), 
and partial cytochrome-b sequences from 
representative exemplars (LHE 1541 and 
AMNH 268938) differ by only about 3.8% 
(J.L. Patton, personal commun.). 
Specimens that we identify as Marmosops 
bishopi were included among the material 
that Anderson (1997) reported as M. impav- 
idus (e.g., UMMZ 156014), M. noctivagus 
keaysit (USNM 579249), and M. parvidens 
(AMNH 268938). 
BOLIVIAN SPECIMENS EXAMINED: Beni, 1 km E 
La Embocada (UMMZ 156014); Cochabamba, 
Cordillera de Mosetenes (CBF 7531); La Paz, 
Alto Rio Madidi (USNM 579249), La Reserva 
(AMNH 268938); Santa Cruz, El Refugio (LHE 
1541, 1553, 1556), San Rafael de Ambor6 (MSB 
55843). 
10 Unfortunately, both of the other specimens we ex- 
amined from eastern Santa Cruz (LHE 1553, 1556) con- 
sist of skulls extracted from rotted specimens found in 
pitfall traps. 
VOSS ET AL.: BOLIVIAN MARMOSOPS 25 
Marmosops impavidus 
The application of the name impavidus is 
problematic because no type material is 
known to exist, and because Tschudi’s (1845) 
original description is diagnostically inade- 
quate (Tate, 1933: 25, 182). Current usage 
dates from Cabrera (1958), who used the bi- 
nomen M. impavidus for the taxon that Tate 
(1933) recognized as M. caucae. Although 
the lost type material is assumed to have 
been collected in the eastern foothills of the 
Peruvian Andes, no exact location was ex- 
plicitly stated in the original description. For 
the purposes of this report, we assume that a 
small series of specimens (AMNH 230017, 
230018, 230020, 230022—230027) collected 
near San Pablo (ca. 10°27'S, 74°52’W; 275 
m above sea level) in the Peruvian depart- 
ment of Pasco represents the typical mor- 
phology. 
This a medium-size species (table 8), larg- 
er than Marmosops bishopi but averaging 
smaller than typical specimens of M. nocti- 
vagus (see Patton et al. [2000] and below). 
The dorsal pelage is dull grayish-brown to 
reddish-brown, with drab (grayish) hues pre- 
dominating among younger specimens and 
warmer (reddish) tones predominating 
among older adults. The ventral pelage of 
most Peruvian and western Brazilian speci- 
mens consists of a median strip of self-white 
or cream-colored fur from chin to anus, bor- 
dered by lateral zones of gray-based fur be- 
tween the fore- and hindlimbs. However, in 
the Peruvian material at hand (which in- 
cludes specimens from Ucayali and Loreto in 
addition to the Pasco sample mentioned 
above) the relative widths of the median self- 
colored and lateral gray-based zones exhibit 
considerable variation. The metapodials are 
covered with pale fur that does not contrast 
abruptly in color with the digits. Tails are 
sometimes indistinctly bicolored (paler be- 
low than above; e.g., AMNH 230017) and 
particolored (paler distally than proximally; 
e.g., AMNH 230027), but other individuals 
have almost unicolored tails (e.g., AMNH 
76531). Adult males have knob-like lateral 
carpal tubercles, but none that we examined 
has a gular gland; the scrotal fur is white and 
the scrotal epithelium is unpigmented. One 
lactating female from Loreto (AMNH 
