Wyonycteris is a genus of small mammals that existed in the late Paleocene and early Eocene epochs. The type species is Wyonycteris chalix, which lived in Wyoming during the Clarkforkian North American Land Mammal Age of the Paleocene and was originally proposed to be an early form of insectivorous bat. Later re-examination of the material has put this alliance in doubt, and the genus has instead been proposed as belonging to the subfamily Placentidentinae, within the family Nyctitheriidae. Similar fossil material of the same time period found in Europe was later discovered and described as new species, Wyonycteris richardi.Smith, Thierry. (1995). Présence du genre Wyonycteris (Mammalia, Lipotyphla) à la limite Paléocène-Eocène en Europe. Comptes Rendus de l Académie des Sciences - Series IIA - Earth and Planetary Science. 321. 923-930.
Secord (2008) described the first known species of Wyonycteris from the Tiffanian NALMA, Wyonycteris galensis and W. microtis, although the status of both species as members of Wyonycteris has been questioned. The two largest species, W. primitivus and W. kingi, are known from the early Eocene of Mississippi and England, respectively.
Evolutionary relationships Wyonycteris is only known from dental remains. It is characterized by W-shaped crests on the outer side of the upper molars, a trait that it shares with most insectivorous bats. However, Wyonycteris possesses a number of additional cusps on the upper molars that are not present in bats leading many researchers to conclude that it is more closely related to the extinct insectivorous family Nyctitheriidae. A recent phylogenetic analysis found most species of Wyonycteris to be within the family Nyctitheriidae, most closely related to the genus Pontifactor. Wyonycteris microtis was found to be very distantly related to the other species of Wyonycteris, outside the family Nyctitheriidae and more closely related mammal to bats alongside genus Eosoricodon.Matthew F. Jones, Nancy Simmons, K. Christopher Beard (2022.) "Relationship of nyctitheres (Mammalia, Nyctitheriidae) to bats and other laurasiatherians", in "The Society of Vertebrate Paleontology 82nd annual meeting"
Rose et al. (2012) compared Wyonycteris to the genus Plagioctenoides and concluded that the two may in fact belong to the same genus. If this is the case, the correct genus name would be Plagioctenoides since it was formally named first.
Distribution Paleocene Tiffanian Polecat Bench Formation, Wyoming Clarkforkian Willwood Formation, Wyoming
Eocene Tienen Formation, Belgium Woolwich and Blackheath Beds Formations, England Argiles d'lignite du Soissonnais Formation, France Wasatchian Tuscahoma Formation, Mississippi Wasatch and Willwood Formations, Wyoming
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