Icaronycteris

...There are more species of chiroptera in Japan than there are rodents, with about 38 species in five families: Pteropodidae, Rhinolophidae, Pteropidae, Vespertilionidae, and Free-tailed bats.
[fossil]
The Eocene Icaronycteris (Icaronycteriidae), which is thought to be the oldest ancestor of bats, has claws on the first and second fingers of its forelimbs and is similar to the macrochiroptera in that its wings are broad, but its molars have sharp projections like those of the microchiroptera, making it intermediate in appearance. It was already flying.

*Some of the terminology that mentions "Icaronycteris" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…日本の翼手類は齧歯類よりも種数が多く，オオコウモリ科，キクガシラコウモリ科，カグラコウモリ科，ヒナコウモリ科，オヒキコウモリ科の5科からなり，約38種。
［化石］
　コウモリの中でもっとも古い祖先とされる始新世のイカロニクテリスIcaronycteris(イカロニクテリス科)は，前肢の第1,2指につめがあり，翼が幅広いところは大翼手類に似るが，臼歯は小翼手類同様に鋭い突起をもち，中間的である。すでに飛翔生活をしていた。…

※「Icaronycteris」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報