Icaronycteris

Icaronycteris is a genus of microchiropteran (echolocating) bat that lived in the early Eocene, approximately 52.2 million years ago, making it the earliest known definitive bat.[1] Four exceptionally preserved specimens, among the best preserved bat fossils, are known from the Green River Formation of North America.[1] There is only one thoroughly described species of bat in the genus, I. index,[2] although fragmentary material from France has also been tentatively placed within Icaronycteris as the second species I. menui.[3] I. sigei is based on well-preserved fragments of dentaries and lower teeth found in Western India.[4]