(Uploaded by Plazi for the Bat Literature Project) Xeronycteris Gregorin and Ditchfield, 2005 is a rare monotypic genus of Lonchophyllinae bats endemic to Brazil, with Xeronycteris vieirai Gregorin and Ditchfield, 2005 as the type and sole species. We updated the geographical distribution of the species, including new records from the Cerrado and the Caatinga. Using traditional and geometric morphometric data obtained from 49 museum specimens, including the type series and those representing new records, we describe and discuss the morphological variation of skull shape found in the most comprehensive sample of X. vieirai to date. We also compare similar species and the geographic distribution of X. vieirai and highlight diagnostic traits useful for field identification. Xeronycteris vieirai is now known to occur in 14 localities confirmed by 54 museum specimens housed in Brazilian scientific collections. Records of this species are sparse, as even 15 years after its discovery the knowledge on this species is based on specimens from only a few localities. Specimens of this species show considerable morphological variation in different regions of the skull, especially for a highly specialized nectar-feeding bat, demonstrating variations in the snout and temporomandibular articulation. We discuss endemism issues related to the different biomes where it occurs (in the South American dry diagonal). We also compare these aspects to other bat species with similar geographic distributions, identifying important elements for future research on this species.