Newly Discovered Amber Fossil Preserved the Oldest Known Prehistoric Tropical Frog

Saturday, 16 June 2018 - 12:40PM
Saturday, 16 June 2018 - 12:40PM
Newly Discovered Amber Fossil Preserved the Oldest Known Prehistoric Tropical Frog
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Flickr/Oregon State University
The Cretaceous period of prehistory is mostly well known for its giant dinosaurs like the Tyrannosaurus rex. Much less well known, but still important, were the smaller tropical frogs also running/hopping around.

Which is what an extinct Electrorana limoae frog was likely doing in modern-day Myanmar before it was tragically and permanently trapped in sticky amber. About 99 million years later, the fossilized amber has been uncovered in northern Myanmar by a team of scientists, who now have extremely well-preserved evidence that frogs lived in wet, tropical forests at this early point in the species' history. The findings were just published in Nature.

Or, "early" in the sense that it's early for us, less so for the frogs. Frogs are thought to be at least as old as 200 million years old, but it's nearly impossible to learn much about the early amphibians - due to their small size and biology, they don't fossilize easily and most of the extinct frog remains are long gone. In particular, we had no way of knowing where frogs lived back then.

Since frogs are such an established tropical species nowadays, it's easy to assume that frogs have always been a tropical species, but this the first evidence scientists have to back that up. Beyond being found in a tropical locale, the fact that the preserved frog is so complete - its skull, body, arms, and hands are all intact - we can get a closer look at just how adapted frogs had already become to their tropical environments.

Other amber fossils found in the area have helped scientists get a sense of the region, and all the mosses, bamboo-like plants, aquatic spiders, and velvet worms point to the region being very tropical during the Cretaceous era. David Blackburn, a co-author on the new research and a herpetologist (he studies amphibians and reptiles) at the Florida Museum of Natural History, said the following in a press release from the museum:

Opening quote
"It's almost unheard of to get a fossil frog from this time period that is small, has preservation of small bones and is mostly three-dimensional. This is pretty special. But what's most exciting about this animal is its context. These frogs were part of a tropical ecosystem that, in some ways, might not have been that different to what we find today – minus the dinosaurs."
Closing quote

There are still questions that need to be answered about this Cretaceous tropical frog. For example, by examining its bone structure, the closest matching frogs alive today are fire-bellied and midwife toads, which live in temperate environments in other parts of the world.

But considering only a literal handful of fossilized frogs in amber have ever been discovered, with the oldest prior one being only 40 million years old, this Electrorana limoae is a great find for amphibian enthusiasts.

Science News