The fossil of Electrorana limoae. (Lida Xing / China Geosciences University)
At first glance, odd-shaped specks that darken a vibrant piece of yellow amber appear to be amorphous spots. But on closer examination, a form emerges.
There are two previous extremities. At the end of each limb there are four smaller bones, which form a shape clearly similar to that of the hands. Within the larger dark spot, which has a rounded top, the eye sockets become distinguishable. It is a skull.
Enclosed within the smooth piece of amber, is the body of a tiny young tropical frog. Scientists say the tiny bug, which is less than an inch long, lived about 99 million years ago before being buried in the sap of the sticky tree. At that time, dinosaurs still roamed the Earth.
The fossil is one of four dating from the Cretaceous period, providing scientists with the earliest direct evidence that frogs inhabited humid tropical forests, according to a statement from the Florida Museum of Natural History . The findings were published Thursday in Nature & # 39; s Scientific Reports.
"It is almost unheard of to get a fossil frog from this time period that is small, has small bone preservation and is mostly three-dimensional," David co-authored the study. Blackburn, badociate curator of herpetology at the Florida Museum of Natural History, said in a statement. "This is very special."
The fossils included a frog skeleton complete enough for scientists to identify it as a new species, called Electrorana limoae according to the study. The other fossils contain two hands and a footprint of a frog that probably rotted inside the amber.
"Honestly, I'm still amazed that there are even frogs found in amber," Blackburn told Gizmodo. "It's a remarkable experience to hold these little gems and see the parts of the frogs that seem to have been there last month."
While frogs have existed for more than 200 million years, their fossil record is thin and usually biased towards species of arid and seasonal environments, not small forest dwellers, the statement says.
But now, with the discovery of the four small lumps of amber originally dug in northern Myanmar, Blackburn said scientists know that frogs have lived in jungle environments for at least 99 million years.
"These frogs were part of a tropical ecosystem that, somehow, could not have been so different from what we found today, except dinosaurs," he said.  In addition to giving scientists a glimpse into the life of ancient frogs, fossils are also the oldest known examples of frogs preserved in amber. Previous fossils were found in the Dominican Republic and date from about 40 million years ago.
The fossils were a "miraculous" finding, said Lida Xing, another study author and paleontologist at the Chinese University of Geosciences in Beijing. News
"In China, frogs, lizards and scorpions are called three treasures of amber," Xing said.
Beyond the rarity of the discovery, fossils are essential to help scientists learn more about the evolutionary history of frogs.
"Our skeleton comparisons of these new frog fossils indicate that these frogs preserved in amber were 'real frogs' and may represent one of the oldest lineages seen today," Blackburn said. a Popular Science.
All they have learned from the tiny remains, Blackburn said there are still many unanswered questions. Many features such as the bones of the wrist, pelvis, hip bones, inner ear and upper part of the spine are used by herpetologists to discover details of a frog's life and determine its relationship to other frogs says the statement. Unfortunately, in recently discovered fossils, those crucial parts either were missing or had not fully developed in the young frog.
Blackburn said he continues to wait for other frogs to be discovered in amber.
"We do not have many communities of frogs of a single species in the forests," he said. "It seems extremely unlikely that there is only one." There could be many more fossils "
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