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Temporal range: Early Eocene
Icaronycteris index.jpg
Icaronycteris index, Green River Formation, in the ROM,
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Chiroptera
Suborder: Microchiroptera
Family: Icaronycteridae
Genus: Icaronycteris
Jepsen 1966

Icaronycteris is an extinct 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]

Icaronycteris index, Houston


Icaronycteris[5] measured about 14 centimetres (5.5 in) long and had a wingspan of 37 centimetres (15 in). It 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. 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.[6]


According to Simmons & Geisler 1998,[7] Icaronycteris is the first genus, followed by Archaeonycteris, Hassianycetris, and Palaeochiropteryx, in a series leading to extant microchiropteran bats.[8]










Microchiroptera (Echolocating bats)


See also[edit]



  1. ^ a b Gunnell & Simmons 2005, Fossil Bats, p. 214
  2. ^ Jepsen 1966
  3. ^ Simmons & Geisler 1998, p. 40[not in citation given]
  4. ^ Smith et al. 2007, Abstract
  5. ^ The name relates the mythic flight of Icarus to Nycteris, the genus of "hollow-faced bats".
  6. ^ Palmer 1999, p. 211
  7. ^ Simmons & Geisler 1998, Abstract
  8. ^ Simmons & Conway 1998, Discussion of Phylogenetic Relationships
  9. ^ Simmons & Conway 1998


Further reading[edit]