But its size _ 10 pounds and 16 inches long _ isn't the only curiosity. Researchers discovered the creature's bones in Madagascar. Yet it seems to be a close relative of normal-sized frogs who today live half a world away in South America, challenging assumptions about ancient geography.
The discovery, led by paleontologist David Krause at New York's Stony Brook University, was published Monday by the journal Proceedings of the National Academy of Sciences.
"This frog, if it has the same habits as its living relatives in South America, was quite voracious," Krause said. "It's even conceivable that it could have taken down some hatchling dinosaurs."
Krause began finding fragments of abnormally large frog bones in Madagascar, off the coast of Africa, in 1993. They dated back to the late Cretaceous period, roughly 70 million years ago, in an area where Krause also was finding dinosaur and crocodile fossils. But only recently did Krause's team assemble enough frog bones to piece together what the creature would have looked like, and weighed.
The largest living frog, the Goliath frog of West Africa, can reach 7 pounds. But Krause teamed with fossil frog experts from University College London to determine that Beelzebufo isn't related to other African frogs.
It seems to be a relative of South American horned frogs, known scientifically as Ceratophrys. Popular as pets, they're sometimes called pacman frogs for their huge mouths.
Like those modern frogs, Beelzebufo had a wide mouth and powerful jaws, plus teeth. Skull bones were extremely thick, with ridges and grooves characteristic of some type of armor or protective shield.
The name comes from the Greek word for devil, Beelzebub, and Latin for toad, bufo (pronounced boo-foe).
The family link raises a paleontology puzzle: Standard theory for how the continents drifted apart show what is now Madagascar would have been long separated by ocean from South America during Beelzebufo's time. And frogs can't survive long in salt water, Krause noted.
He contends the giant frog provides evidence for competing theories that some bridge still connected the land masses that late in time, perhaps via an Antarctica that was much warmer than today.