Using 26 cranial measurements, we conducted a morphometric study on 113 adult skulls of the currently recognized rabbits Sylvilagus brasiliensis and S. sanctaemartae from Colombia, Ecuador, and Peru. Five morphological groups are identified of which 4 warrant species-level recognition. North and west of the Andes, S. gabbi occupies the lowlands of northern Colombia and northwestern Ecuador. Sylvilagus sanctaemartae is morphologically indistinguishable from S. gabbi and is a synonym of it. Two species live in the Andes of Colombia: S. fulvescens in the Western and Central Andes and S. apollinaris in the Eastern Andes. East of the Andes, Sylvilagus brasiliensis defilippi is found in the tropical Orinoco and Amazon basins of Colombia, Ecuador, and Peru, and S. brasiliensis andinus occurs in the Andes of Ecuador. These 2 subspecies intergrade in the Amotape-Huancabamba Zone of extreme southern Ecuador and adjacent west-central Peru. The eastern distributional limit of S. b. defilippi outside the study area in South America is unknown. An additional 50 skulls of S. gabbi and 14 of S. dicei were examined from Costa Rica and Panama to compare with the rabbits from South America. The data show that S. gabbi exhibits no noticeable geographic variation from Central America to northern Colombia and northwestern Ecuador. Sylvilagus dicei from the Cordillera de Talamanca of Costa Rica and Panama is morphologically most similar to S. fulvescens from the Western and Central Andes of Colombia and they are likely closely related. Methods are presented to identify all taxa and the distribution of each taxon is provided. This taxonomic arrangement is based on few specimens. Accordingly, species boundaries and phylogenetic relationships should be tested by focusing future collecting and morphological and molecular research in high-priority areas such as: 1) along the Colombian–Ecuadorian border from the Pacific Coast, across the Andes into the Amazon Basin; 2) Amotape-Huancabamba Zone of Ecuador and Peru; and 3) Eastern Andes of Colombia.
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Vol. 98 • No. 6