26 
AMERICAN MUSEUM NOVITATES 
NO. 3466 
TABLE 8 
Measurements (mm) and Weights (g) of Peruvian and Bolivian Specimens of Marmosops impavidus 



Peru Bolivia 
AMNH AMNH AMNH AMNH AMNH MSB 
230017 230020 230025 230027 230026 57002 
Sex female female male male unknown male 
HBL 124 109 130 115 — 110 
LT 141 — 150 132 — 147 
HF 18 — 19 18 — 17 
Ear 18 — 20 19 — 20 
CBL 31.1 30.5 33.0 30.6 34.3 31.4 
NB 4.1 3.7 4.3 4.2 4.4 3.7 
LIB 5.8 5.8 5.8 5.7 6.3 5.6 
ZB — 16.0 16.6 16.6 — 16.3 
PL 17.8 17.4 18.9 17.4 19.7 18.1 
PB 10.6 9.9 9.8 10.2 10.7 9.7 
MTR 13.0 13.8 14.0 12.7 14.0 12.7 
LM 6.6 6.7 6.6 6.4 6.8 6.4 
M1-M3 5.7 5.7 5.6 5.6 5.8 5.4 
WM4 2.5 2.3 2.3 2.5 2.4 2.4 
Weight 34 — — 49 — 25 


272709) has 3—1—3 = 7 mammae, but anoth- 
er from the same locality (AMNH 273151) 
has 4—1—4 = 9; all of the teats in both in- 
dividuals are abdominal/inguinal. 
In craniodental morphology, Marmosops 
impavidus can be distinguished from other 
Bolivian congeners by the absence of supra- 
orbital beads (usually distinct in M. noctiva- 
gus); presence of a shallow but usually dis- 
tinct postorbital constriction (usually absent in 
M. noctivagus); presence of palatine fenestrae 
(absent in M. bishopi); absence of accessory 
upper canine cusps (present in M. bishopi); 
and very small, usually conical bullae. 
The sole Bolivian specimen that we iden- 
tify as Marmosops impavidus is MSB 57002, 
which was collected sympatrically with M. 
noctivagus at Palmira in the lowlands of Pan- 
do department (fig. 12). This specimen has 
redder dorsal fur and narrower nasals than do 
most Peruvian specimens, but its morpholo- 
gy is otherwise a good match with topotyp- 
ical (Peruvian) material. Other Bolivian 
specimens previously referred to this species, 
however, appear to represent different taxa. 
Anderson (1997: 153) reported two spec- 
imens identified as Marmosops impavidus 
from Incachaca in Cochabamba department, 
but cited only one by catalog number 
(AMNH 38718); the specimen in question is 
a juvenile whose broken skull (originally 
miscataloged as 38711) exhibits incipient su- 
praorbital beading, very short canines, and 
small molars (LM = 6.3 mm), traits that 
closely match Tate’s (1933) description of 
yungasensis—a taxon that we consider to be 
a junior synonym of M. noctivagus (see be- 
low). Two other Bolivian specimens explic- 
itly identified by Anderson as M. impavidus 
are UMMZ 126680 (from 20 km NNE Car- 
anavi, in La Paz department) and UMMZ 
156014 (from 1 km E La Embocada, in Beni 
department). The former is a subadult whose 
lack of supraorbital beading is possibly due 
to immaturity, but whose lack of a postorbital 
constriction more closely resembles the ma- 
terial we refer to M. noctivagus (see below). 
UMMZ 156014, however, is an example of 
M. bishopi (see above). The only additional 
material that Anderson referred to M. impav- 
idus consists of MSB 57000 (from Indepen- 
dencia in Pando department) and MSB 
58508 (from 2 km S Caranda in Santa Cruz 
department); both are examples of “Graci- 
linanus”’ unduaviensis, a taxon that is cur- 
rently treated (e.g., by Gardner, 1993) as a 
junior synonym of G. agilis. 
BOLIVIAN SPECIMENS EXAMINED: Pando, Palmira 
(MSB 57002). 
