18 AMERICAN MUSEUM NOVITATES NO. 3963 
based on its dark brown wings and considerably smaller size in all dimensions (e.g., FA = 
36.0-40.5 mm; mass = 6.0-9.0 g.; CBL = 13.0-15.0 mm; CIL = 14.0-15.2 mm; Koopman, 1994; 
Monadjem et al., 2010). 
Myotis (subgenus Chrysopteron) species with yellow or orange dorsal fur and dichromatic 
orange and black wings are not limited to Africa, but also occur in Asia. At least six Asian 
species (M. bartelsi, M. formosus, M. hermani, M. rufoniger, M. rufopictus, and M. weberi) 
exhibit color patterns with dichromatic wing pigmentation superficially similar to that of M. 
nimbaensis (Csorba et al., 2014). Csorba et al. (2014) gave diagnoses and measurements of 
these species that provide a basis for distinguishing them from M. nimbaensis. These authors 
recognized two pelage and skin color patterns among the Asian species: a “rufoniger type” and 
a “formosus type.’ Species exhibiting “rufoniger type” morphology include M. bartelsi, M. her- 
mani, M, rufoniger, and M. weberi. These species can be distinguished from M. nimbaensis 
based on darker dorsal pelage that has four bands of color (individual dorsal hairs black basally, 
pale yellow distally, then darkening to deep red before terminating in a black tip; Csorba et al., 
2014) rather than the bright orange tricolored dorsal fur of M. nimbaensis. Species with “rufo- 
niger type” coloration are also considerably darker ventrally than M. nimbaensis, having hairs 
with a black base, followed by either a pale yellowish section that progressively darkens distally 
to deep red, or are otherwise entirely deep red (Csorba et al., 2014). The ear is also edged with 
black in rufoniger-type species (Csorba et al., 2014), a trait lacking in M. nimbaensis (or any 
other African species of Chrysopteron). The thumb and underside of hind foot are entirely black 
in species with “rufoniger type” coloration (Csorba et al., 2014) but not in M. nimbaensis, which 
has an orange-brown thumb and a brown foot. Myotis rufoniger has flight membranes with a 
broad band of red that extends from the ankle to the forearm along the side of the body, and 
black pigmentation is limited to the more distal and posterior portions of the plagiopatagium 
(Bhak et al., 2017). In contrast, the black pigment is more extensive in M. nimbaensis, extend- 
ing much closer to the body including reaching the tibia and into the membrane behind the 
humerus, and the pale portions of the wings are more orange than red. 
Members of the Myotis rufoniger group vary somewhat in size, but they are all large bats 
roughly comparable in size to M. nimbaensis. Measured forearm lengths of M. rufoniger (FA = 
45.0-56,0; Csorba et al., 2014) overlap with those of M. nimbaensis, but cranial dimensions of 
M. rufoniger (e.g., GLS = 16.98-19.24 mm; ZB = 10.04-12.24 mm) do not overlap, with M. 
nimbaensis being the slightly larger species. Dental morphology is also somewhat different; M. 
rufoniger has a P3 that is roughly two thirds the size of P2 and which is usually in line with the 
other check teeth (rarely displaced lingually; Csorba et al., 2014), compared with M. nim- 
baensis, in which P3 is less than half the size of P2 and is lingually displaced. Considerable 
overlap in most dimensions exists between M. nimbaensis and M. weberi (FA = 49.7-53.5 mm; 
GLS = 19.15-19.72 mm; ZB = 12.37-12.67 mm; Csorba et al., 2014). However, M. weberi as 
described by Csorba et al. (2014) can be distinguished by having a relatively short upper canine 
that is only about 1.5x the height of P4 (C height is ~2x height of P4 in M. nimbaensis) anda 
p3 that is no more than half the basal area of p2 (p3 is at least three quarters the basal area of 
p2 in M. nimbaensis). 
