US researchers have unearthed a fossil arm bone from a coquí frog, also known as rain frog, dating back to 29 million years. According to a study, which was published in the Biology Letters journal on Wednesday, the ancient coquí makes it the world’s oldest, surpassing the amber frog fossil discovered in the Dominican Republic in 1987. David Blackburn, Florida Museum curator of herpetology and the study's lead author, said ...