The Collections Of Mammals Made In The 1950s By The Serviço Nacional De Peste (National Plague Service) In North-Eastern Brazil Include Some 240 Specimens Of Climbing Mice, Genus Rhipidomys, From The States Of Ceará And Pernambuco. Morphological And Morphometric Analyses Reveal The Presence Among Them Of A New Species, Rhipidomys Cariri Sp.Nov., Described Herein With Two Subspecies, Namely The Nominotypical Subspecies And R. Cariri Baturiteensis Ssp.Nov., Respectively From The Mesic Enclaves Of Cariri And Baturité Within The Semi-Arid Caatinga Of Ceará. The Species May Be Distinguished From Both The Population Of R. Mastacalis Found In Eastern Pernambuco And That Of R. Macrurus Occurring In The Serra De Ibiapaba On The Western Border Of Ceará Through Its Larger Body Size, Greyer And Coarser Pelage, Longer Vibrissae And Larger Molars. Although The Separation Of The Enclaves From The Atlantic Forest To The East And The Amazonian Forest To The West Probably Dates Back Only To The Mid-Holocene Or Late Pleistocene, The New Endemic Species May Well Have A Much More Remote Origin; Molecular Data Would Be Needed To Test This Hypothesis.
