More than a third of the 7,000-odd living species of frogs and toads are found in rain forests around the world. But the fossil record for amphibians from these kinds of wet, tropical environments has been almost nonexistent, leaving paleontologists with few clues to their early evolution.

Now, lumps of amber dating back to the Cretaceous period have revealed a set of four tiny tropical frogs that lived alongside the dinosaurs, making them the oldest frog fossils of their kind. The specimens include the remains of an ancient frog complete enough to be described as a new species, called Electrorana limoae.

“It was exhilarating to hold these small fossils up to the light to reveal the frogs within,” says