Palaeochiropterygidae
Palaeochiropterygidae is a family of extinct bats. It was originally erected by the Swiss naturalist Pierre Revilliod in 1917 after discoveries of "Palaeochiropteryx" fossils from the Messel Pit of Germany. Palaeochiropterygidae was merged into Archaeonycteridae by Kurten and Anderson in 1980, but modern authorities specializing in bat fossils maintain the distinction between the two. It was classified to the unranked clade Microchiropteramorpha by Smith "et al." in 2007. They existed from the Ypresian to the Lutetian ages of the Middle Eocene epoch (55.8 to 40.4 million years ago). Paleobiology. Two species of Palaeochiropterygidae, "Palaeochiropteryx tupaiodon" and "P. spiegeli", are  known from complete skeletons from the famous Messel Pit fossil deposits in Germany. "Palaeochiropteryx tupaiodon" is the most common mammal found at Messel. All other species belonging to Palaeochiropterygidae are known only from isolated teeth and jaw fragments from Europe, India, Turkey, and possibly North America. At Messel, the two species of "Palaeochiropteryx" are hypothesized to have occupied similar niches to living hipposiderids and rhinolophids that forage close to the ground and among vegetation. Wings with low aspect ratio and wing loading and preserved stomach contents of small moths and caddisflies support the idea that these palaeochiropterygids were slow but  maneuverable fliers. The widespread distribution of Palaeochiropterygidae among the northern continents in the early and middle Eocene conflicts with the known morphology of "P. tupaiodon" and "P. spiegeli", however, suggesting that other species of palaeochiropterygids had body plans much more suitable to long distance dispersal. Evolutionary relationships. Palaeochiropterygidae are generally considered to be the most advanced of the early bat families. Phylogenetic analyses have consistently shown Palaeochiropterygidae to be the closest relatives of the living, or crown, groups of bats. Most phylogenetic analyses only include species of fossil bats known from complete skeletons, so relationships of species within Palaeochiropterygidae are  currently unknown. Both "Matthesia" and "Cecilionycteris" may be junior synonyms of "Palaeochiropteryx". "Stehlinia" has been previously considered to be a member of the superfamily Vespertilionoidea, possibly aligned with Natalidae or Kerivoulidae, but is now more commonly recognized as a palaeochiropterygid. "Stehlinia", along with "Lapichiropteryx" and "Anatolianycteris", possesses a very simple lower fourth premolar compared to other palaeochiropterygids and a close relationship between those three species has been proposed. Genera. It contains the following genera. The list may be incomplete or inaccurate: