2004 






Fig. 8. Palatal morphology in Marmosops 
noctivagus (A, AMNH 262403) and Gracilinanus 
agilis (B, MVZ 197437) illustrating generic dif- 
ferences in patterns of fenestration. Both Mar- 
mosops and Gracilinanus have incisive foramina 
(if), posterolateral palatal foramina (plpf), and 
maxillopalatine fenestrae (mp); in addition, some 
species of Marmosops and all Gracilinanus have 
palatine fenestrae (p). Maxillary fenestrae (m), 
however, are present only in Gracilinanus. Scale 
bars equal 5 mm. 
VOSS ET AL.: BOLIVIAN MARMOSOPS | He, 
present as a cluster of larger and smaller 
openings between the maxillopalatine fenes- 
trae and the postpalatine torus. The alisphe- 
noid tympanic wings (auditory bullae) are 
large, almost hemispherical capsules without 
ventral processes or lateral constrictions. The 
upper canine lacks accessory cusps, and the 
last upper molar is not much wider (trans- 
verse dimension) than M3 and is approxi- 
mately triangular in outline. 
MORPHOLOGICAL COMPARISONS: Marmo- 
sops creightoni is the only known brownish- 
furred species of the genus to lack whitish 
thoracic or abdominal markings; all others 
have at least some white or cream-colored 
midventral fur that contrasts abruptly with 
the darker color of the dorsum and flanks.’ 
In many species, whitish midventral fur 
(which may be either self-colored or gray- 
based) extends continuously from chin to 
anus, but in a few Amazonian and northern 
Andean forms (e.g., M. neblina; see Gardner, 
1990: fig. 2) whitish midventral markings are 
narrow and sometimes discontinuous. Al- 
though narrow whitish midventral markings 
might occur polymorphically in larger sam- 
ples of M. creightoni, the six examples at 
hand suggest that most individuals have 
completely dark venters. 
Qualitative and morphometric compari- 
sons with other Bolivian congeners (the iden- 
tification and taxonomy of which are dis- 
cussed below) reveal many additional differ- 
ences (table 4). Marmosops bishopi, for ex- 
ample, is much smaller than M. creightoni, 
has dull reddish- or grayish-brown (versus 
rich chocolate-brown) dorsal fur, has pale- 
furred metapodials that do not contrast in 
color with the digits (versus dark-furred me- 
tapodials contrasting with whitish digits), 
does not have a pale tail-tip (versus pale tail- 
tip present), lacks palatine fenestrae (versus 
palatine fenestrae present), and has a small 
posterior accessory cusp on the upper canine 
(versus upper canine without accessory 
cusps). Also, adult males of M. bishopi usu- 
ally lack a gular gland (versus gular gland 
weakly developed), have large bladelike 
(versus knobby) lateral carpal tubercles, and 
7 Marmosops invictus, a small Panamanian species 
with blackish-gray fur, has dark underparts that are only 
superficially washed with white. 
