2004 
lacrimal foramina of Bolivian species are 
usually concealed from lateral view inside 
the orbit); and M. paulensis has very long 
incisive foramina that extend posteriorly be- 
hind the canine alveoli (the incisive foramina 
are substantially shorter in all Bolivian taxa). 
These and other taxonomically informative 
characters merit uniform scoring for phylo- 
genetic analysis in any comprehensive at- 
tempt to revise the contents of Marmosops, 
but such exercises are beyond the scope of 
this preliminary report. 
MOLECULAR COMPARISONS: The first 680 
base-pairs of the mitochondrial cytochrome- 
b gene were sequenced from the holotype of 
Marmosops creightoni by J.L. Patton, whose 
generosity in sharing these data allowed us 
to make preliminary comparisons with ho- 
mologous didelphid sequences previously 
obtained by his laboratory (Patton et al., 
1996; Mustrangi and Patton, 1997; Patton et 
al., 2000). In order to assess the relationships 
of M. creightoni with other congeneric 
forms, we assembled a small dataset repre- 
senting nine species of Marmosops, and we 
included Gracilinanus microtarsus as an out- 
group (table 5). We selected exemplar hap- 
lotypes based on sequence length (the lon- 
gest available sequence for each species was 
chosen), previous representation in published 
reports (Patton et al., 1996; Mustrangi and 
Patton, 1997; Patton et al., 2000), and acces- 
sibility of cataloged morphological voucher 
material in museums. Most species are rep- 
resented by single haplotypes in our analysis, 
but we included three sequences from geo- 
graphically divergent samples of M. nocti- 
vagus to assess molecular variation within a 
geographically widespread taxon. 
As quantified by pairwise uncorrected se- 
quence divergence (table 6), Marmosops 
creightoni is phenetically most similar to M. 
noctivagus, from which it differs on average 
by about 9.7%. Interestingly, of the three an- 
alyzed haplotypes of the latter species, M. 
creightoni is most divergent (10.9%) from 
the geographically proximal Bolivian sample 
and least divergent (9.2%) from each of the 
Peruvian and Brazilian specimens. All other 
pairwise interspecific comparisons in these 
results are >10% divergent, with the excep- 
tion of a relatively small value (5.7%) be- 
tween M. impavidus and M. ocellatus. 
VOSS ET AL.: BOLIVIAN MARMOSOPS 19 
A. branch-and-bound parsimony analysis 
of the nucleotide sequence data (implement- 
ed with PAUP 4.0b10; Swofford, 1998) re- 
covered a single minimum-length tree with 
two main clades (fig. 11), one of which con- 
sists of Marmosops creightoni, M. impavi- 
dus, M. noctivagus, and M. ocellatus in the 
sequence (noctivagus (creightoni (impavidus 
+ ocellatus))). The other clade contains 
members of the parvidens complex (M. bish- 
opi and M. parvidens), two southeastern Bra- 
zilian forms (M. incanus and M. paulensis), 
and the Amazonian species M. neblina. Un- 
fortunately, there is only weak Bremer and 
bootstrap support for several branches in this 
topology, notably including all of those that 
resolve the relationships of creightoni with 
other congeneric forms. 
NATURAL History: All of our material of 
Marmosops creightoni was collected in the 
valley of the Rio Zongo, one of the principal 
headwaters of the Rio Beni on the eastern 
slopes of the Cordillera Real. The Valle de 
Zongo descends precipitously from 4800 to 
<900 m above sea level, with flanking slopes 
that are often in excess of 60°. The climate 
is very humid, with clouds and mist each 
morning and afternoon for most of the year. 
Between 2000 and 3000 m above sea level— 
the known elevational range of M. creighto- 
ni—the natural vegetation of the Valle de 
Zongo is humid montane (“‘cloud’’) forest.® 
Habitat information associated with speci- 
mens of M. creightoni taken at three locali- 
ties in the Valle de Zongo is summarized be- 
low, in order of their collection dates. 
The five paratypes that G.K. Creighton 
collected in 1979 were taken at two localities 
along a road that descends the valley and 
provides access to a series of hydroelectric 
generating stations, power lines, and support 
facilities. His first collecting site was at Cu- 
8 We use the nontechnical term ‘“‘cloud forest’? for 
montane rainforests generally, including the formations 
that Grubb (1977) usefully defined as Lower Montane 
Rain Forest, Upper Montane Rain Forest, and Subalpine 
Rain Forest. Synonyms used by Bolivian botanists in- 
clude “‘Ceja de Monte de Yungas’’ (corresponding to 
Subalpine Rainforest; e.g., at Cuticucho) and “‘Bosque 
Htimedo Montafioso de Yungas”’ (corresponding to Up- 
per Montane Rainforest; e.g., at Saynani). For a critical 
review of “cloud forest’? and its technical synonyms 
from a field zoologist’s point of view, see Myers (1969); 
for another (botanical) perspective, see Webster (1995). 
