Nicholas J. Czaplewski

Vampire bats likely first appeared in South America in the early Miocene (~20 Ma) and evolved to feed upon the blood of native South American mammals of medium to large body size, in particular, xenarthrans–ground sloths, armadillos, pampatheres, and glyptodonts, and native ungulates–notoungulates and litopterns. Following the formation of the Panamanian Isthmus (~5 Ma), vampire bats immigrated into North America as participants in the Great American Biotic Interchange, following their preferred prey species, probably xenarthrans. The earliest records of vampire bats are the extinct species Desmodus archaeodaptes from three early Pleistocene faunas in Florida. The large extinct vampire D. stocki occurs in 18 late Pleistocene faunas in the southern US and Mexico. The giant extinct vampire D. draculae is known from eight late Pleistocene faunas from Mexico and Belize south to Brazil and Argentina. The late Pleistocene extinction of D. draculae and D. stocki coincided with the extinction of their primary source of blood, the mammalian megafauna. The common vampire bat D. rotundus survived and now occurs throughout tropical America because it had a broader prey base, feeding on the blood of a variety of medium- to large-sized mammals, and currently preying preferentially on non-native domestic livestock.

We document rare finds of fossil bats from two localities representing the Pleistocene epoch in southern and central Nebraska, Albert Ahrens locality (No-104, late Irvingtonian age, Middle Pleistocene), Nuckolls County, and Litchfield (Sm-102, late Rancholabrean age, latest Pleistocene), Sherman County. The Albert Ahrens local fauna with strong boreal influence has produced two bats, Lasiurus cf. borealis and Cf. Myotis sp. The Litchfield local fauna, also showing a strong boreal influence, has yielded two bats, Eptesicus fuscus and Cf. Myotis, among a diverse Pleistocene fauna of small vertebrates and a pollen record indicating a boreal mixed conifer and deciduous woodland, contrasting with the grassland and mixed grass prairie of the area in historic times prior to anthropogenic conversion. The vertebrate fauna from the Litchfield site can be assigned to the Rancholabrean land mammal age based on the presence of Bison, on faunal correlation, and on several extralimital taxa of small mammals. The fossil bat taxa are widespread in North America and still extant in Nebraska today; their glacial stage occurrences in a nonkarstic (caveless) region is consistent with previous interpretations of the Albert Ahrens and Litchfield local faunas as indicating cool equable climates and wooded parkland environments. These are the first bats to be reported from each of the respective paleofaunas.

We report three new taxa of bats from the late early Eocene to earliest middle Eocene (Bridgerian biochrons Br1b–Br2; ca. 50–48 Ma) Elderberry Canyon Quarry, Sheep Pass Formation, in the Egan Mountain Range of eastern Nevada, USA. Volactrix simmonsae gen. et sp. nov., represented by two dentaries, is tentatively referred to the family ?Onychonycteridae and exhibits a p3 that is much smaller than the p2, a semimolariform p4, and lower molars with a postcristid configuration intermediate between necromantodonty and nyctalodonty. The genus Palaeochiropteryx, a palaeochiropterygid otherwise known from the early and middle Eocene of Europe, is the first representative of its genus and of the family Palaeochiropterygidae outside Eurasia and the Indo-Pakistan subcontinent. Palaeochiropteryx is represented at the site by a partial skeleton with a crushed skull and two left dentaries (one unexposed within the same limestone block but revealed by micro-computed tomography scanning) and is formally named Palaeochiropteryx sambuceus sp. nov. A third taxon, Sonor handae gen. et sp. nov., is a probable vespertilionid, evidenced by a dentary fragment with double-rooted p3 and myotodont lower molar morphology, and provides the earliest occurrence of the family Vespertilionidae in the Western Hemisphere. Despite the small number of specimens, these three new taxa comprise the most diverse Eocene assemblage of bats yet found in a single quarry in the Western Hemisphere.

With 14 species recorded, the Miocene La Venta bat fauna is the most diverse bat paleocommunity in South America. It includes the oldest plant-visiting bat in the New World and some of the earliest representatives of the extant families Phyllostomidae, Thyropteridae, and Noctilionidae. La Venta's Notonycteris magdalenensis is an extinct member of the subfamily Phyllostominae, a group of modern Neotropical animalivorous bats, and is commonly included in studies of the evolution of Neotropical bats, but aspects of its biology remain unclear. In this study, we used multivariate dental topography analysis (DTA) to reconstruct the diet of N. magdalenensis by quantitatively comparing measures of molar complexity with those of 25 modern noctilionoid species representing all major dietary habits in bats. We found clear differences in molar complexity between dietary guilds, indicating that DTA is potentially an informative tool to study bat ecomorphology. Our results suggest N. magdalenensis was probably an omnivore or insectivore, rather than a carnivore like its modern relatives Chrotopterus auritus and Vampyrum spectrum . Also, we reconstructed the body mass of N. magdalenensis to be ~95 g, larger than most insectivorous bats, but smaller than the largest carnivorous bat ( V. spectrum ). Our results confirm that N. magdalenensis was not a specialized carnivore. It remains to be demonstrated that the specialized carnivory ecological niche was occupied by the same lineage of phyllostomines from at least the middle Miocene. Combining our diet and body-mass reconstructions, we suggest that N. magdalenensis exhibits morphological pre-adaptations crucial for the evolution of specialized carnivory.

The middle Miocene La Venta bat fauna is the most diverse bat palaeocommunity in South America, with at least 14 species recorded. They include the oldest plant-visiting bat in the New World, and some of the earliest representatives of the extant families Phyllostomidae, Thyropteridae and Noctilionidae. La Venta’s Notonycteris magdalenensis is an extinct member of the subfamily Phyllostominae, a group of modern Neotropical animalivorous and omnivorous bats, and is commonly included in studies of the evolution of Neotropical bats, but aspects of its biology remain unclear. In this study, we used a multivariate dental topography analysis (DTA) to reconstruct the likely diet of N. magdalenensis by quantitatively comparing measures of molar complexity with that of 25 modern phyllostomid and noctilionid species representing all major dietary habits in bats. We found clear differences in molar complexity between dietary guilds, indicating that DTA is potentially an informative tool to study bat ecomorphology. Our results suggest N. magdalenensis was probably an omnivore or insectivore, rather than a carnivore like its modern relatives Chrotopterus auritus and Vampryum spectrum . Also, we reconstructed the body mass of N. magdalenensis to be ∼50 g, which is larger than most insectivorous bats, but smaller than most carnivorous bats. Our results confirm that Notonycteris magdalenensis was probably not a specialised carnivore. It remains to be demonstrated that the specialised carnivory ecological niche was occupied by the same lineage of phyllostomines from at least the middle Miocene. Combining our diet and body mass reconstructions, we suggest that N. magdalenensis exhibits morphological pre-adaptations crucial for the evolution of specialised carnivory.