National Geographic : 2015 Dec
SOUTH AMERICA Fossil site URUGUAY Paca-rana Josephoartigasia monesi Science EXPLORE ART: RAÚL MARTÍN. GRAPHICS: NGM ART. SOURCES: PHILIP COX; ANDRÉS RINDERKNECHT; ERNESTO BLANCO It’s Big, and It Bites Scientists analyzing the skull of the largest known rodent have determined that the prehistoric herbivore’s front bite was as strong as a tiger’s. What’s more, its curved, foot-long incisors could withstand forces three times as powerful as the force its jaw muscles could generate. The conclusion? This distant cousin of the guinea pig “must have been doing something more with those teeth than just eating with them,” says anatomist Philip Cox. At an estimated weight of 2,200 pounds, Josephoartigasia monesi likely didn’t face too many threats as it lumbered through the estuaries and deltas of South America more than two million years ago. Cox and his colleagues suspect that J. monesi relied on its front teeth for sparring with rivals and defending itself against predators, as well as for rooting in the ground for food. “That would make the teeth quite like the tusks of an elephant,” Cox says. The beast’s size made one other use of its teeth less probable, he says: A rodent roughly five feet tall and ten feet long is almost certainly “too big to be digging burrows.” — Rachel Hartigan Shea Only one fossil of J. monesi has been discovered. The paca-rana is its closest living relative.