Distributional records of mammals from the southwestern Yucatan Peninsula of Mexico

Records of mammals are reported for the Mexican States of Campeche and Tabasco on the Yucatán Península. New distributional records inelude: Uroderma bllobatum, and Micronycteris megalotis from Campeche; and Myotis elegans, Sylvilagus floridanus, Heteromys gaumeri, and Oryzomys fulvescens from Tabasco. Additional information also is provided on the occurrence of Cryptotis nigrescens in Campeche and Rhynchonycteris naso in eastem Tabasco. Based on specimens reported in this study, the southwestemmost limit of the Yucatán Biotic Province, as it applies to mammals, is defined as that area of Tabasco north of the Sierra del Norte de Chiapas and east of the Río Usumacinta. The Mexican portion of the Yucatán Península (see Fig. 1) is an area of mammalian endemism with a fauna that diífers markedly from the rest of México; however, few extensive field studies on mammals of this región have been conducted and distributional limits of this endemic fauna are not well understood. The most comprehensive studies of the peninsular mammalian fauna were a distributional monograph by Gaumer (1917) and a series of annotated checklists by Jones et al. (1973, 1974a, 1974b) and Genoways and Jones (1975). Other papers also have added to our knowledge of mammalian distributions on the Yucatán Península, including those by Hatt (1938, 1953), Hatt and Villa-R. (1950), Jones and Lawlor (1965), Bimey et al. (1974), Sanchez-H. et al. (1986), and McCarthy (1987). Our field work was designed to determine the distributional limits of mammals on the Península and to examine the transition between the nuclear Middle American mammal fauna and that of the Yucatán Península. Although the Mexican State of Tabasco often is not included in distributional studies of the Península, our initial fieldwork indicated that the portion of Tabasco east of the Río Usumacinta and north of the Sierra del Norte de Chiapas contained a characteristic peninsular mammalian fauna. Consequently, this eastem section of Tabasco is considered herein to represent the southwestemmost extensión of the Yucatán Biotic Province (for definition and discussion of this biotic province, see Goldman and Moore, 1945; Barrera, 1962). Fieldwork for this study was conducted during July and August of 1980 and 1984. Specimens representing six new records for the Mexican States of Campeche and Tabasco are reported. Information also is included for two species previously reported from Campeche and Tabasco. ' Department of Biological Sciences, Fordham University, Bronx, New York 10458. 2 Department of Biology, Angelo State University, San Angelo, Texas 76909. Submitted 19 November 1987. Introduction