Fossil Evidence and the Origin of Bats |
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Authors: | Gregg F Gunnell Nancy B Simmons |
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Institution: | (1) Museum of Paleontology, University of Michigan, 1109 Geddes Avenue, Ann Arbor, Michigan 48109-1079, USA;(2) Division of Vertebrate Zoology, Department of Mammalogy, American Museum of Natural History, New York, New York, USA |
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Abstract: | The phylogenetic and geographic origins of bats (Chiroptera) remain unknown. The earliest confirmed records of bats date from
the early Eocene (approximately 51 Ma) in North America with other early Eocene bat taxa also being represented from Europe,
Africa, and Australia. Where known, skeletons of these early taxa indicate that many of the anatomical specializations characteristic
of bats had already been achieved by the early Eocene, including forelimb and manus elongation in conjunction with structural
changes in the pectoral skeleton, hind limb reorientation, and the presence of rudimentary echolocating abilities. By the
middle Eocene, the diversification of bats was well underway with many modern families being represented among fossil forms.
A new phylogenetic analysis indicates that several early fossil bats are consecutive sister taxa to the extant crown group
(including megabats), and suggests a single origin for the order, at least by the late Paleocene. Although morphological studies
have long placed bats in the Grandorder Archonta, (along with primates dermopterans, and tree shrews), recent molecular studies
have refuted this hypothesis, instead strongly supporting placement of bats in Laurasiatheria. Primitively, proto-bats were
likely insectivorous, under-branch hangers and elementary gliders that exploited terminal branch habitats. Recent work has
indicated that a number of other mammalian groups began to exploit similar arboreal, terminal branch habitats in the Paleocene,
including multituberculates, eulipotyphlans, dermopterans, and plesiadapiforms. This may offer an ecological explanation for
morphological convergences that led to the erroneous inclusion of bats within Archonta: ancestral archontan groups as well
as proto-bats apparently were exploiting similar arboreal habitats, which may have led to concurrent development of homoplasic
morphological attributes. |
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Keywords: | bats phylogeny origins Chiroptera Archonta Lipotyphla Paleocene |
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