Microcebus margotmarshae is a small mouse lemur with a head-body length of about 11–12 cm, a tail length of about 14 cm, a total length of 25–26 cm, and a body weight of 41–50 g (Louis et al., 2008). The dorsal and tail pelage is predominantly reddish-orange with gray undertones, the ventral fur is white to cream, and the head is largely bright reddish-orange. The muzzle and the area surrounding the eyes are light brown, and there is a small, bright white spot on the nose ridge between the eyes. The ears are small (Louis et al., 2008).
As of 2010, this species had not been studied in the wild.
Northwestern Madagascar. This newly-described species is currently known only from its type locality, the Antafondro Classified Forest south of the Andranomalaza River and north of the Maevarano River (Andriantompohavana et al., 2006; Louis et al., 2008). Further research is needed to determine the precise limits of its distribution (Louis et al., 2008). Formerly, the mouse lemurs from this region were thought to be M. sambiranensis.
The conservation status of this species has not yet been assessed. It is present in the Antafondro Classified Forest, and possibly at high-elevations in the Tsaratanana Special Reserve as well (Louis et al., 2008).
As of 2010, M. margotmarshae was not being kept in captivity (I. J. Porton, pers. comm.).
The only confirmed locality for this species is in the Antafondro Classified Forest (Louis et al., 2008).