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Icaronycteris gunnelli is the oldest bat species described to date

Close-up of the fossilized skeleton ofIcaronycteris Gunnelli. This specimen is part of the research collections of the United States Museum of Natural History.

Photo: AMNH/Mick Ellison

Paleontologists have discovered many bat fossils in these early Eocene sediments in recent decades. So far, their work has allowed them to be classified into only two types:

  • Its name was first identified in 1966 Icaronycteris index
  • The second was determined in the 2008 year named Onychonycteris finneyi.

This species was described thanks to nearly complete skeletons discovered in fossil lake sediments, and is the smallest in the Green River Lake system. To date, no bats have been detected in other lakes of the formation.

The lowlands of the Fossil Lake Basin were warm and humid, similar to a subtropical environmentExplain the authors of this work published in the journal Plus one (A new window) (in English) who adds that The basin was surrounded by highlands and mountains, where plants of more temperate climates could be found.

A specimen of Icaronycteris Gunnelli.

sample fromIcaronycteris Gunnelli From the Royal Ontario Museum

Photo: Royal Ontario Museum


  • The bat is a nocturnal mammal of the Chiroptera order.
  • There are about 1,400 species in the world, grouped into 175 genera and 20 families.
  • They represent the fifth of the 6,500 known species of mammals, the second largest group after rodents.
  • They are found all over the world except for the polar regions and a few remote islands.
  • At least 17 species live in Canada, including 8 in Quebec.

Given the very wide diversity of bat species observed in many ecosystems of our time, some paleontologists believe that the habitats in the Green River region must reflect this reality of the past.

Such is the case of bat specialist Nancy Simmons, of the United States Museum of Natural History in New York, who was involved in describing the second. I always thought the Green River area should have more bat speciesThe scientist explains in a press release released by the American Museum.

Dutch colleagues from the Naturalis Biodiversity Center shared this view, so they re-analyzed the fossil group ofIcaronycteris index Updated since 1966.

A very large number of bats have been identified as Icaronycteris indexand we wondered if there were, in fact, several species among these specimens. »

Quote from Tim Rietbergen, evolutionary biologist at Naturalis

Additionally, as part of their work, Tim Rittbergen and his colleagues learned of an exceptionally well-preserved fossil skeleton, which the museum acquired in 2017 from a private collector.

Comparisons with other fossils are clear: the specimen belongs to a different species. In addition, analysis of another fossil skeleton, discovered in 1994 and part of the collections of the Royal Ontario Museum in Canada, confirmed that it belonged to the same unknown species.

The latter is named Icaronycteris Gunnelli To highlight the work of paleontologist Greg Gunnell, who died in 2017, who made a significant contribution to understanding bat evolution.

Outstanding development

It should be noted that bats are the only mammals capable of flight, an adaptation that appeared very early in their evolution.

In addition, scientists believe that green river bats evolved independently of other Eocene species. Finding these fossils helps us better understand what happened during the early evolution of these mammalsMr. Rietbergen notes.