Rhipidomys mastacalis (Lund 1840) [Rhipidomys] mastacalis (Lund 1840), K. Dansk. Vid. Selsk. Naturv. Math. Afhandl.: 24. Type Locality: Brazil, Minas Gerais State, Rio das Velhas, Lagoa Santa. Vernacular Names: Atlantic Forest Rhipidomys. Synonyms: Rhipidomys leucodactylus (Wagner 1845); Rhipidomys maculipes (Pictet and Pictet 1844). Distribution: Atlantic Forest region, SE Brazil (Pernambuco to São Paulo). Conservation: IUCN – Lower Risk (lc). Discussion: R. leucodactylus section sensu Tribe (1996). Comprehending the definition and distribution of Lund’s mastacalis stands at the center of systematic problems involving medium-sized rhipidomys with whitish venters. As broadly conceived by Cabrera (1961), the form contained, as subspecies or complete synonyms, the following taxa now associated with other species: R. emiliae, R. macrurus, R. nitela (including fervidus and yuruanus), tenuicauda (= R. fulviventer), and R. venezuelae (see individual accounts). The restricted concept of the species, as currently understood, circumscribes yet another form endemic to the Atlantic Forest zone, SE Brazil. Although the morphological distinction between R. macrurus and R. mastacalis is not well marked (Tribe, 1996), chromosomal studies consistently reveal populations with low (48-52) versus high (74-80) fundamental numbers, respectively (2n = 44 in all; Andrades-Miranda et al., 2002 a; Svartman and Almeida, 1993; Zanchin et al., 1992 a). The distributions of the two in SE Brazil appear to intertwine in complex fashion; other species are likely involved as noted by Tribe (1996), who cited many specimens as cf. macrurus or as species indeterminate.

Published as part of Wilson, Don E. & Reeder, DeeAnn, 2005, Order Rodentia - Family Cricetidae, pp. 955-1189 in Mammal Species of the World: a Taxonomic and Geographic Reference (3 rd Edition), Volume 2, Baltimore :The Johns Hopkins University Press on page 1170, DOI: 10.5281/zenodo.7316535