For nearly two centuries, its existence remained little more than a scientific hypothesis. Now, researchers have finally reconstructed the identity and appearance of Ocnotherium giganteum, one of the giant mammals that once roamed South America during the Pleistocene era.
The breakthrough comes from an international study led by paleontologist François Pujos of Argentina’s CONICET research council, with contributions from the University of Milan and the University of Buenos Aires. The findings, published in the Zoological Journal of the Linnean Society, are based on newly discovered fossils recovered from caves in the Brazilian state of Minas Gerais.
The species had first attracted scientific attention in the mid-19th century, when a handful of isolated teeth were found in the region. At the time, researchers suspected they belonged to a prehistoric sloth, but the remains were too limited to confirm the animal’s identity.
Thanks to newly analyzed material - including an almost complete skull and several partial skeletons - scientists were able to reconstruct around 90 percent of the animal’s anatomy from at least eight individuals. The study describes a massive mammal weighing close to two tons, with a particularly robust skull and a distinctive dentition.
Researchers believe the animal mainly moved on all fours but could also rise onto its hind legs when threatened, adopting a semi-upright posture to defend itself from predators. Beyond revealing the appearance and behavior of Ocnotherium giganteum, the study sheds new light on South America’s rich Pleistocene fauna before the extinction of many large mammals around 12,000 years ago.