''Icaronycteris'' is an extinct genus of microchiropteran (echolocating)

bat Bats are flying mammals of the order Chiroptera (). With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most birds, flying with their very long spread-out ...

that lived in the early

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

, approximately , making it the earliest bat genus known from complete skeletons, and the earliest known bat from North America. Multiple exceptionally preserved specimens, among the best preserved bat fossils, are known from the

Green River Formation The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day Green River (Colorado River), Green River in Colorado, Wyoming, and Utah. The sedimen ...

of North America. The best known species is ''I. index.'' Fragmentary material from France has also been tentatively placed within ''Icaronycteris'' as the second species ''I. menui''. ''I. sigei'' is based on well-preserved fragments of dentaries and lower teeth found in

Western India Western India is a loosely defined region of India consisting of western states of India, Republic of India. The Ministry of Home Affairs (India), Ministry of Home Affairs in its Western Zonal Council Administrative divisions of India, Adminis ...

. In 2023, the species ''I. gunnelli'' also from the Green River Formation was distinguished from ''I. index'', and ''I. menui'' and ''I. sigei'' were proposed to be removed from the genus due to them not being closely related.

Description

''Icaronycteris'' measured about long and had a wingspan of . ''Icaronycteris'' closely resembled modern bats, but had some primitive traits. The tail was much longer and not connected to the hind legs with a skin membrane, the first wing finger bore a claw and the body was more flexible. Similarly, it had a full set of relatively unspecialised teeth, similar to those of a modern

shrew Shrews ( family Soricidae) are small mole-like mammals classified in the order Eulipotyphla. True shrews are not to be confused with treeshrews, otter shrews, elephant shrews, West Indies shrews, or marsupial shrews, which belong to dif ...

. Its anatomy suggests that, like modern bats, ''Icaronycteris'' slept while hanging upside down, holding onto a tree branch or stone ridge with its hind legs.

Phylogeny

According to , ''Icaronycteris'' is the most basally diverging genus, followed by '' Archaeonycteris'', '' Hassianycetris'', and ''

Palaeochiropteryx ''Palaeochiropteryx'' ( ) is an extinct genus of bat from the Lutetian, Middle Eocene of Europe and North America. It contains three very similar species – ''Palaeochiropteryx tupaiodon'' and ''Palaeochiropteryx spiegeli'', both from the famous ...

'', in a series leading to extant microchiropteran bats. found ''

Onychonycteris ''Onychonycteris'' was the more primitive of the three oldest bat, bats known from complete skeletons, having lived in the area that is current day Wyoming during the Eocene period, 52.5 million years ago. Taxonomy Two specimens of ''Onychonyct ...

'' to be sister to the North American species of ''Icaronycteris''. This position was supported by Jones et al. (2024), who found ''Icaronycteris index'' and ''I. gunnelli'' among a clade including ''Xylonycteris stenodon'', ''Icaronycteris''? ''menui'', ''Archaeonycteris''? ''storchi'', ''Archaeonycteris brailloni'', and ''Protonycteris gunnelli'' (Icaronycteridae sensu lato). Sister to the Icaronycteridae clade was a clade comprised of nearly all known members of Onychonycteridae. ''Icaronycteris''? ''sigei'' was recovered well outside of Icaronycteridae in the latter study, falling sister to members of Archaeonycteridae.

References

Notes

Sources

* * * * * * * *

Description

Phylogeny

See also

References

Notes

Sources

Further reading