Two fossilized bat skeletons found in western Wyoming represent a new species and are the oldest set of bat bones ever discovered, researchers say.
Unbelievable full of fossils Icaronycteris gunnelli which show all the animal bones in a realistic position, come from limestone rocks that accumulated as lake sediments about 52.5 million years ago, vertebrate paleontologist Tim Rietbergen and colleagues report April 12 in PLOS ONE . Skeletons of several other species of bats, including another of the genus Icaronycteris found in the same limestones, called the Green River Formation, are preserved at least 40 centimeters above the new fossils—and are therefore younger.
But it’s hard to estimate how much younger these fossils are because researchers don’t know how quickly the sediments accumulated over time, says Rietbergen of the Naturalis Biodiversity Center in Leiden, the Netherlands.
Analysis of newly discovered skeletons shows that I . gunnelli — a kind of rune. According to Rietbergen and his colleagues, the wingspan of this species, which is usually measured by the length of the forearm bones, is almost 7 percent smaller than that of its closest known bat relative. During his life I. gunnelli weighed somewhere between 22.5 and 28.9 grams—about half as much as a tennis ball, the team estimated.
The skeletons “are a big discovery,” says Zhe-Xi Luo, a vertebrate paleontologist at the University of Chicago who was not involved in the study. The location of the bones on the legs I. gunnelli suggests that it, like many modern bats, hung upside down while roosting, he says.
Because the skeletons are so similar to those of some modern bats, “we’re no closer to knowing what kind of creature bats evolved from,” says Brock Fenton, a vertebrate paleontologist at the University of Western Ontario in Canada, who was also not involved in the work. . The world’s oldest known bats lived about 56 million years ago, but the fossils of these species are mostly individual teeth rather than whole skeletons.