Minas Gerais – For nearly two centuries, its existence had remained only a hypothesis. Now, paleontology has finally given a face and a story to one of the most remarkable creatures of South American megafauna: Ocnotherium giganteum. In the mid-19th century, a few isolated teeth were discovered in caves in Minas Gerais, Brazil. Some researchers speculated they might belong to a Pleistocene sloth, but the attribution remained uncertain. Today, a new international study has, for the first time, reconstructed the identity and biology of Ocnotherium giganteum. The research was coordinated by paleontologist François Pujos of CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas) in Buenos Aires, with contributions from Dawid Adam Iurino, professor of vertebrate paleontology at the University of Milan, and paleontologist Alberto Boscaini, researcher at the Institute of Ecology, Genetics and Evolution of the University of Buenos Aires. Published in the Zoological Journal of the Linnean Society, the study resolved the mystery thanks to new fossil finds, including an almost complete skull and partial skeletons recovered during expeditions in Brazilian caves led by paleontologist Càstor Cartelle of the Pontifícia Universidade Católica of Minas Gerais. The researchers were able to analyze remains from at least eight individuals, reconstructing around 90% of the animal’s skeletal anatomy. The resulting profile describes a massive mammal weighing nearly two tons, with an exceptionally robust skull and a distinctive dentition. Skeletal analysis suggests it moved mainly on all fours, but was also capable of rearing up on its hind limbs into a semi-upright posture, likely as a defensive behavior against predators. “This work not only confirms that Ocnotherium giganteum is a distinct species, clearly differentiating it from better-known relatives such as Mylodon or Megatherium, but also identifies it as an endemic species unique to Brazil’s Atlantic coast,” said Alberto Boscaini. “Digital analyses of 3D models allowed us, for the first time, to understand many anatomical details of this giant, offering valuable insights into its biology and ecology. For instance, the olfactory bulbs appear extremely developed, suggesting that the animal relied on a highly refined sense of smell to navigate its environment, locate conspecifics and predators, or find food sources,” explained Professor Dawid Adam Iurino, who conducted tomographic analyses of the fossils, exploring internal cranial structures—such as the brain, inner ear, nerves, and blood vessels—without damaging the specimens and revealing previously unknown paleobiological features. A particularly significant detail emerges from the study of a humerus currently under analysis, which bears cut marks. “The incisions observed on the bone indicate that this giant was most likely butchered and consumed by early Homo sapiens who arrived on the continent, confirming direct interaction between humans and megafauna in Pleistocene Brazil,” concludes François Pujos. Beyond reconstructing its appearance and ecology, the study contributes to a broader understanding of the richness of South American Pleistocene fauna and its significance in the context of early Homo sapiens dispersal, prior to the extinction of large mammals around 12,000 years ago. (9colonne)