It's been called the "devil frog" and the "armoured frog from hell", but those English labels don't quite capture the delightfully sinister ring of its genus name: Beelzebufo. (Bufo=toad; Beelzebub – well, you know who he is.)

First described in 2008, Beelzebufo ampinga was an oversized and well-armoured frog of Late Cretaceous Madagascar, with some estimates putting its weight at around 4.5 kilograms (10 pounds) – that's heftier than the heftiest of living anurans (frogs and toads), the goliath frog of West Africa. From the start, palaeontologists pegged this prehistoric amphibian-beast, on the scene some 65 to 70 million years ago, as a potentially very formidable predator, based on its heft and big-mouthed architecture alone. Now, a new analysis clarifies just how formidable the creature may have been.

In a paper just published in Scientific Reports, a team of American, British and Australian scientists estimated Beelzebufo's potential chomping power by measuring the bite force of the present-day Cranwell's horned frog. This species belongs to the genus Ceratophrys: the well-known South American horned frogs, also nicknamed "Pacman frogs' or "hopping heads" for their whopping mouths. These amphibians are morphologically very similar to the "devil frog" of bygone Madagascar.

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South American horned frogs, also known as the Pacman frogs, have tremendous bite force. Image: Kristopher Lappin

Whereas most living frogs have pretty weak jaws, relying mainly on tongue action to catch and subdue small prey, Ceratophrys species boast a heavier-duty bite thanks to disproportionately broad and short heads, robust skulls, big jaw-adductor muscles and sharp, recurved teeth with thick bases (plus a pair of genuine fangs). Such business-end anatomy allows the sit-and-wait hunters to tackle prey as large as lizards, birds and small mammals.

After measuring the biting oomph of different-sized Cranwell's horned frogs using a force transducer, the researchers scaled up to estimate the bite force of both a very big museum specimen of another Ceratophrys species, the Brazilian horned frog, and the extinct titan Beelzebufo – reasonable given the similar shape and proportions of the frogs' heads and jaw musculature.

The results postulate that a large Beelzebufo with a head width of 154 millimetres could exert about 2,214 newtons (N) – some 226 kilograms-force (498 pounds-force) – at the midpoint of its jaws. That's comparable to the bite force of the biggest of big cats, lions and tigers, and exceeds by up to 25 percent that of a crocodilian of the same head width.

A jaw-punch of that magnitude would, the scientists speculate, put such respectable quarry as small crocodiles on the devil frog's potential menu. The rock of Madagascar's Maevarano Formation, from which Beelzebufo was discovered, has also yielded fossils of diverse dinosaur neighbours such as the little theropod Rahonavis. "At this bite force, Beelzebufo would have been capable of subduing the small and juvenile dinosaurs that shared its environment," the University of Adelaide's Dr Marc Jones, one of the authors of the study, said in a press release.

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An artist's depiction of Beelzebufo ampinga munching on a small theropod dinosaur. Image: Nobu Tamura/Wikimedia Commons

It's certainly intriguing to imagine Beelzebufo employing the same explosive ambush strategy as today's South American horned frogs: just replace snakes and rodents with unwary dino hatchlings.

"This is the first time bite force has been measured in a frog," Professor Kristopher Lappin of California State Polytechnic University-Pomona, the study's lead author, said in the press release. "And, speaking from experience, horned frogs have quite an impressive bite, and they tend to not let go. The bite of a large Beelzebufo would have been remarkable, definitely not something I would want to experience firsthand."



Top header image: Roger Le Guen/Flickr