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Evolution

The delicate skeletons of bats do not fossilise well; it is estimated that only 12% of bat genera that lived have been found in the fossil record. Most of the oldest known bat fossils were already very similar to modern microbats, such as Archaeopteropus (32 million years ago). The oldest known bat fossils include Archaeonycteris praecursor and Altaynycteris aurora (55-56 million years ago), both known only from isolated teeth. The oldest complete bat skeleton is Icaronycteris gunnelli (52 million years ago), known from two skeletons discovered in Wyoming. The extinct bats Palaeochiropteryx tupaiodon and Hassianycteris kumari, both of which lived 48 million years ago, are the first fossil mammals whose colouration has been discovered: both were reddish-brown.

Bats were formerly grouped in the superorder Archonta, along with the treeshrews (Scandentia), colugos (Dermoptera), and primates. Modern genetic evidence now places bats in the superorder Laurasiatheria, with its sister taxon as Ferungulata, which includes carnivorans, pangolins, odd-toed ungulates, even-toed ungulates, and cetaceans. One study places Chiroptera as a sister taxon to odd-toed ungulates (Perissodactyla).

The flying primate hypothesis proposed that when adaptations to flight are removed, megabats are allied to primates by anatomical features not shared with microbats and thus flight evolved twice in mammals. Genetic studies have strongly supported the monophyly of bats and the single origin of mammal flight.