Published online 18 February 2008 | Nature | doi:10.1038/news.2008.607

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'Frog from hell' fossil hints at later split of continents.

Beelzebufo (left) was 2-3 times bigger than the largest living South American frog in this family (top right), and 4-5 times bigger than the largest living Malagasy frog (bottom right). PNAS

A giant frog that hopped around Madagascar 65–70 million years ago has been discovered.

Fossil fragments show that the frog, called Beelzebufo ampinga, could have measured 20 centimetres across its squat head, and probably more than 40 centimetres from snout to tail. The researchers nicknamed the monstrous beast ‘the frog from hell’; the official name comes from one of the many names for the devil (Beelzebub) and the Latin for 'toad' (bufo).

Strangely, the frog looks to be more similar to a subfamily of amphibians called the Ceratophryinae, thought to be endemic to South America, than to any of the hundreds of frog species of present-day Madagascar.

It is thought that the supercontinent called Gondwana, made up of Antarctica, South America, Africa, Madagascar, the Indian subcontinent, and Australia and New Zealand, began to split apart some 160 million years ago. But the Beelzebufo fossils support the controversial notion that parts of the supercontinent stayed together until much later than that, says Susan Evans, a vertebrate morphologist and palaeontologist at University College London, UK.

Evans suspects that Beelzebufo and current day Ceratophryinae in South America had a common Gondwanan ancestor that began to diversify before 70 million years ago, and that Madagascar-India was linked by land to South America via Antarctica as recently as 80 million years ago, in the Late Cretaceous period. Evans and her colleagues report the find in this week’s Proceedings of the National Academy of Sciences1.

Puzzle pieces

Artist's impression of the 'frog from hell'. Stony Brook University

Evans and her colleagues studied more than 60 frog fossil fragments collected in the Mahajanga Basin in Madagascar. The team couldn’t piece together a complete skeleton, but did get a nearly complete picture of the skull, which was “short and fat with a huge mouth", says Evans.

Similarly-shaped South American frogs have a strong bite and can feast on small vertebrate such as mice and lizards: “Basically, they eat anything smaller that walks by,” Evans says.

Beelzebufo was 2-3 times bigger than Ceratophrys aurita, the largest living South American frog in this family, and 4-5 times bigger than the largest living Malagasy frog, Mantidactylus guttulatus.

Stuck together

Evans says that when she first began to suspect the Madagascar fragments came from a frog related to South American Ceratophryinae, she was very cautious about the claim. “We knew it would be controversial,” she says. “There are people who believe everything on Madagascar today must have been there when it broke with Gondwana 160 million years ago.”

Blair Hedges, a biologist at Pennsylvania State University in University Park, agrees that Beelzebufo is an important find. “The new fossil frog, besides being large and odd-shaped, is quite unexpected because of its apparent relationship with South American species,” he says.

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But he says he isn’t yet convinced that the new find is related to the South American frogs. Molecular clock data suggests that these frogs split from a common ancestor more recently than 66 million years ago, he says. "Based on molecular evidence of frog relationships, the specific resemblance to some living wide-mouthed frogs is more likely from [evolutionary] convergence than actual relationship." Convergent evolution, where unrelated species occupying similar niches tend to look the same, is common in frogs, he says.

Even if they are related, he adds, this doesn't mean that the frogs necessarily had to walk on land from one location to another before Gondwana split. “Any organism, including a frog, can raft on dead vegetation,” he says.

But Evans is convinced they are related: "It is the same family. I have no doubt of that," she says.