Species of Cryptonanus were first described in 1931 by George Henry Hamilton Tate,Voss et al., 2005, p. 5 who described Marmosa microtarsus guahybae (now Cryptonanus guahybae) as a subspecies of Marmosa microtarsus (now Gracilinanus microtarsus), Marmosa agilis chacoensis (now Cryptonanus chacoensis) as a subspecies of Marmosa agilis (now Gracilinanus agilis),Tate, 1931, p. 10 and Marmosa unduaviensis (now Cryptonanus unduaviensis) as a separate species.Tate, 1931, p. 11 In 1943, another species was described, Marmosa agricolai (now Cryptonanus agricolai).Gardner, 2009, p. 41 Species of Cryptonanus were then included in a broadly defined genus Marmosa until the genus Gracilinanus was described in 1989. The fifth currently recognized Cryptonanus species, C. ignitus, was described as a species of Gracilinanus in 2002. At that time, the species of Cryptonanus were variously regarded as separate species or as synonyms or subspecies of other species of Gracilinanus.Gardner, 2009, p. 40
