The scientific community knows of the existence, at present, without counting the fossils, of more than 1,400 species of bats (bats). That is, approximately 20% of the species of mammals that inhabit the Earth are members of this order of animals without feathers but with the ability to fly (among many other abilities). Excluding the polar areas, bats are present in virtually every corner of the planet.
And they are not newcomers... A new study led by scientists from the United States and the Netherlands has discovered the existence of a species of bat (unknown until now) that inhabited the current part of Wyoming (United States) of the Formation Green River approximately 52.5 million years ago.
The team responsible for this research, with Professor Tim Rietbergen (Leiden Biodiversity Center, The Netherlands) as the first author, believes that it is the oldest known bat species and that its discovery helps explain the rapid expansion and diversification of these flying mammals. The results of this work have been published in the journal PLOS One (April 12).
The new species has been given the scientific name Icaronycteris gunnelli, in honor and recognition of Professor Gregg F. Gunell, a paleontologist at Duke University who died in 2017 and made extensive contributions to the understanding of fossil bats and evolution.
The Green River Formation, between Wyoming, Utah, and Colorado, is an important deposit of early Eocene fossils, in which scientists have discovered more than 30 bat fossils in the past 60 years. Until now it was thought that all the specimens belonged to a single species, or two at most, but now it has been possible to establish the existence of a hitherto unknown variety.
"Bats have been known from the Eocene of the Green River Formation since the 1960s. But interestingly, most of the specimens that have emerged from that formation were identified as representatives of a single species, Icaronycteris index, until about 20 years ago, when a second species of bat belonging to another genus," explained Nancy Simmons, co-author of the study and a researcher at the American Museum of Natural History. Despite these historical data, "I always suspected that there should be even more species there," Simmons explains in statements released by the museum where she works, where the remains of the fossil in question are kept.
In recent years, scientists in the Netherlands began to take a close look at Icaronycteris fossils by collecting measurements and other data from museum specimens.
"Paleontologists have collected many bats that have been identified as Icaronycteris index, and we wondered if there were actually multiple species among these specimens," said Tim Rietbergen, Naturalis evolutionary biologist.
The exceptionally well-preserved skeleton that has been key to describing the new species was collected by a private collector in 2017 and purchased by the American Museum of Natural History. When the researchers acquired the fossil with Rietbergen's extensive dataset, it clearly stood out as a new species.
A second fossil skeleton discovered in the same quarry in 1994 and in the collections of the Royal Ontario Museum was also identified as this new species.
"The Fossil Lake deposits of the Green River Formation are simply amazing because the conditions that created the paper-thin limestone layers also preserved almost everything that settled to the bottom of the lake," said Arvid Aase, manager of the Fossil Lake. park and curator of Fossil Butte National Monument in Wyoming. "One of these bat specimens was found lower in the section than all other bats, making this species older than any of the other bat species recovered from this deposit."
"This is a step forward in understanding what happened in terms of evolution and diversity in the early days of bats," concludes Nancy Simmons.
