Late Pleistocene Shrews and Bats (Mammalia: Soricomorpha and Chiroptera) From Térapa, a Neotropical-Nearctic Transitional Locality in Sonora, Mexico

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Two species of shrews and four species of bats are described for Late Pleistocene fossils from Térapa, Sonora, Mexico. Shrews include Notiosorex and an indeterminate genus and species of Soricidae. Bats include several vespertilionids (Lasiurus, Antrozous pallidus, and Myotis) and a molossid (Tadarida brasiliensis). Previous interpretations based on evidence from sediments and other fossils at Térapa suggested the Late Pleistocene presence of a riparian corridor that was wetter and more tropical than at present, including a slow-moving stream, riparian forest, ponded water, marsh, and savanna, or a submerged to emergent grassland. Vertebrate fossils including a crocodylian, certain birds, and a capybara supported the more-tropical interpretation for these habitats. The bats and shrews in the Pleistocene paleofauna support these inferred paleohabitats but only weakly support the more-tropical aspect. Only one bat (Tadarida brasiliensis) has largely tropical biogeographic affinities; the others are widespread or temperate-zone taxa. None of the Neotropical families Phyllostomidae, Mormoopidae, or Natalidae that presently occur in the vicinity of Térapa are yet represented by fossils there. This fact might reflect a nonanalog Late Pleistocene fauna or might simply be due to the general rarity of bat and shrew fossils in fluvio-lacustrine deposits.