This is an amphibian that you wouldn't want to meet in a dark alley: Beelzebufo, a monster fossil frog from Cretaceous sediments in Madagascar. It resembles the ceratophryine family of horned toads (sometimes dubbed "pac man frogs") that are now unique to South America, which the authors of a new study published in the Proceedings of the National Academy of Sciences.

Here, artist Luci Betti-Nash's whimiscal painting of Beelzebufo has it facing extant species Mantidactylus guttulatus, the largest frog in modern-day Madagascar.

The discovery of the big croaker suggests that South America and Madagascar were linked landmasses for much later than previously deduced from other lines of evidence. However, the newly-implied gap in time is substantial. Previously, it was inferred that the two landmasses separated 120 million years ago (Aptian), but the interpretation of this new fossil is that it must have been after 80 million years ago (Campanian). I'm not sure I buy that huge jump in separation dates based on a single genus of fossil frog: 40 million years is a substantial amount of time. On the other hand, sometimes "small" pieces of evidence like this lead to the development of new paradigms in scientific thinking. It has the potential to be the proverbial thread which unravels the sweater.

My caution: It's important to remember that fossils which resemble one another don't necessarily imply a continuous population: there's convergent evolution to consider, as well as the possibility of a highly conserved morphology over time. Both of these phenomena could maintain similar looking populations of "pac-man-esque" frogs on unconnected landmasses. And, I suppose, there's even the less-likely possibility of a "rafting" incident, where a few individuals ride a mass of vegetation across the ocean(s) from South America to Madagascar well after the two have separated. It happened to iguanas, after all: getting from South America to the Galapagos. Actually, with amphibians, their eggs can sometimes hitch a ride on bird feet too, colonizing distant new areas with ease. I'd like to know more about the presence or absence of relevant fossil frogs in Africa during the Cretaceous in order to better evaluate this new interpretation.

Read more about it in this New Scientist article. (I couldn't find the "cited" original article in PNAS, for some reason.)

Labels: amphibians, evolution, fossils, plate tectonics