Frogs trapped in amber for 99 million years are giving a glimpse of a lost world.
The small creatures have been preserved in sticky tree resin since the end of the Age of the Dinosaurs.
The four fossils give a window to a world in which frogs and toads evolved in the rainforests.
Amber from Myanmar, which contains skin, scales, skins, feathers or even entire creatures, is considered a treasure by paleontologists.
Dr. Lida Xing of China University of Geosciences in Beijing said it was a "miraculous" find
"In China, frogs, lizards and scorpions are called three treasures of amber," he told BBC News.
"These amber fossils provide direct evidence that frogs inhabited humid tropical forests before the mass extinction event at the end of the Cretaceous."
The fossil record of the first amphibians is scarce, which makes the discovery particularly valuable to science.
Dr. David Blackmore of the University of Florida, who worked on the fossils with Dr. Xing, said he was small and lived in a tropical forest, so the probability of ending up in the fossil record is "quite low" "
"Frogs have existed on Earth for approximately 200 million years," he said.
"How long have they been associated with these moist forests? Is it a recent or ancient phenomenon?" These fossils of amber frog indicate that this association dates back at least 100 million years ago.
New piece of the puzzle
The four specimens provide a record of the life in the forests of what is now the state of Kachin, Myanmar, during the Cretaceous.
In addition to the frogs, which researchers have called Electrorana limoa, found plants, spiders and insects.
There were even marine molluscs, suggesting that the frogs lived in an ecosystem of warm, humid tropical forest that contained freshwater lakes.
Dr. Ricardo Perez-De-La Fuente, of the Oxford Museum of Natural History, who is not part of the research team, said that each new finding adds a piece to the puzzle.
"The new frog species is a relevant piece of this exciting riddle, a possible top predator of the fossil insects that my colleagues and I study so passionately," he said.
Electrorana has similarities to modern frogs and toads, including the belly of fire toads and midwife toads.
Full details are published in the Scientific Reports journal.
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