Abstract Cyttarops alecto is a rare bat, poorly recorded along its distribu-tional range. In this paper, we report the fi rst record of C. alecto for the western Brazilian Amazon, provide information on dis-tribution and morphological variation of the species along with taxonomic comments based on comparisons of our specimen with the previous information reported in the literature, and we reinterpret the precise type locality for the species.Keywords: Brazil; distribution; emballonurids; Rond o nia; western Amazonia. The subtribe Diclidurina (Chiroptera: Emballonuridae) is confi ned to the Neotropical region and contains eight gen-era (Lim 2007 ). The monotypic genus and species Cyttarops consecutive nights near potential prey for vampire bats, such alecto (Thomas 1913 ), the smoky sheath-tailed short-eared bat, is medium-sized (forearm 45 – 47 mm) with a blackish gray, long, and silky dorsal pelage. Cyttarops has a greatly expanded clavicle, a deeply grooved tibia, and has no wing sac (Jones and Hood 1993 ). Cyttarops alecto is a rare bat, poorly recorded in its distri-butional range, and most captures of the species are of single individuals (Hood and Gardner 2007 , Velazco et al. 2011 ). Although documented by few specimens in collections, this species is broadly distributed in the Neotropical lowlands. The collecting localities of this species are distributed from Nicaragua to Panama, in Central America (Starrett and de and Langtimm 1993 , Jung et al. 2007 ), southwards in South America to eastern Colombia, northern Bolivia, and central Peru (Ochoa et al. 1994 , Aguirre et al. 2010 , Velazco et al. 2011 ) and eastwards to Guiana Shield localities in Guyana, French Guiana, and Suriname (Thomas 1913 , Masson and Cosson 1992 , Lim 2009 ) to the northern state of Par a , Brazil (the type locality), and southern Amazonian Brazil at the Tocantins River Basin (Nunes et al. 2006 ) (Figure 1 ). Herein, we report the fi rst record of