The newest and the oldest: this bat is both. Just first described in PLoS Oneby Dutch paleontologist Tim Rietbergen, is this one Icaronycteris gunnelli the most recently discovered fossil bat species. And at the same time, its age of 52.2 million years also makes it the oldest.
Because although more fossil bats of roughly the same age have turned up in the American state of Wyoming over the past 50 years, this specimen was just a bit deeper in the stratigraphy – and therefore also just a bit further back on the geological time scale. Moreover, those earlier finds always involved either Icaronycteris indexor om Onychonycteris finneyi. Rietbergen actually discovered a new species, bringing the number of known early bat species from the early Eocene (between 56 and 47.6 million years ago) to three.
For his current research, Rietbergen studied two fossils that had been found before but had not yet been studied in detail. He did that himself: he and colleagues looked at 568 different bat characteristics, in extinct and still living species. He compared, among other things, dental characteristics.
So he came to the conclusion that Icaronycteris gunnelli differed enough from other fossils to constitute a separate genus. In fact, two other fossils, from France and India, which previous researchers also believed belonged to the Icaronycteridae, appear to have been misidentified on the basis of his findings.
Today, more than 1,400 species of bats live worldwide. It is likely that the first bats were not good fliers, and simply climbed trees to hover from there, as flying squirrels do today.
Much is still unknown about their early evolution – for example, whether they first developed their ability to fly, or their ability to echolocation, which uses high-pitched sounds (inaudible to the human ear) to track down prey insects. One of the other Eocene species, Onychonycteris finneyi has been used in the past by various scientists to support one hypothesis as well as the other. The discovery of new ancient bat fossils could help to gain more clarity.
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