Fossil “Frog From Hell” Gets a New Look

The fossil frog Beelzebufo was all mouth. Or as close to it as an amphibian can get while still making space for legs and all those other essential parts. That’s the image put forward in a new PLoS One study by University College London paleontologist Susan Evans and colleagues that has substantially revised the appearance and size of the famous fossil frog.

Evans and coauthors named Beelzebufo in 2008. Initially estimated to be about sixteen inches long and weigh about ten pounds, Beelzebufo was a contender for the largest frog of all time. But the frog’s potential diet is what really drew headlines. Pieced together from fossil fragments found in Madagascar’s 65-70 million year old rock, Beelzebufo had lived among some of the last non-avian dinosaurs. And given the frog’s size, it wasn’t a stretch to imagine the imposing anuran leaping out from the undergrowth to nab unwary baby dinosaurs.

[Beelzebufo nabs some dinosaurian dinner in this clip from Dinotasia. Jump to 4:09 for Beelzebufo.]

Based on the original description, early restorations of Beelzebufo looked like a pumped up version of the Surinam horned frog (a grouchy-looking amphibian found in South America). That made sense given the frog’s relatively close relationship to such “Pacman frogs” living today. But with recently-discovered, articulated parts of the skull, backbone, and hindlimb, Evans and colleagues have found that Beelzebufo was “even more bizarre and heavily armoured than earlier reconstructions depicted.”

The new Beelzebufo reconstruction looks like a set of legs meant to propel a huge skull.  Measuring about six inches across the back and three inches long, the frog had a short, wide head fitted with small, plate-like teeth along the jaws. With a skull like that, Beelzebufo likely ambushed and engulfed whatever prey would fit into its mouth. But, contrary to earlier estimates, the big-mouthed anuran may not have been large enough to consume infant Majungasaurus.

Using measurements from the Brazilian horned frog to plug some skeletal gaps, Evans and coauthors estimate that the most complete Beelzebufo yet found was only about seven and a half inches long. There’s scrappy evidence for bigger Beelzebufo that may have been about nine inches long, and different individuals likely reached disparate adult sizes, but the frog wasn’t so monstrous as the globular, dinosaur-chomping glutton that made headlines six years ago.

Nevertheless, the new, more complete fossil material has allowed Evans and colleagues to gain a better understanding of how Beezlebufo survived in Cretaceous Madagascar. The frog was too heavily-built to hop, and instead walked over a landscape that experienced harsh swings between the wet and dry seasons. And given similarities between Beelzebufo and its living relatives in South America, Evans and coauthors propose that the fossil frog likely burrowed into the soil to escape the heat.

“Beelzebufo may have spent the hottest, driest periods fully or partially buried, possibly within a cocoon, as do many arid-adapted living anurans,” Evans and coauthors write, “emerging to feed and reproduce during periods of wetter and/or cooler conditions.” Finding direct evidence of such behavior is going to be tricky, especially for a species mostly known from disarticulated bits and pieces, but the hypothesis brings up a new vision that flips the frog’s reputation as the terror of small dinosaurs. Perhaps, while in their dry season slumber, estivating Beelzebufo were juicy snacks for little Majungasaurus in search of food and water. The devil frog might have been emergency dinosaur chow.

References:

Evans, S., Jones, M., Krause, D. 2008. A giant frog with South American affinities from thee Late Cretaceous of Madagascar. PNAS. 105, 8: 2951-2956

Evans, S., Groenke, J., Jones, M., Turner, A., Krause, D. 2014. New material of Beelzebufo, a hyperossified frog (Amphibia: Anura) from the Late Cretaceous of MadagascarNew material of Beelzebufo, a hyperossified frog (Amphibia: Anura) from the Late Cretaceous of MadagascarNew material of Beelzebufo, a hyperossified frog (Amphibia: Anura) from the Late Cretaceous of Madagascar. PLoS One. 9, 1: e87236.