One morning in 1997, fruit seller Ademir Frare and his 12-year-old nephew Luiz Augusto dos Santos Frare were on one of their regular walks around the rural fields of Cândido Rodrigues, in São Paulo state. The pair had a passion for fossil hunting, so they were left with mouths agape when they came across a bone. Immediately, they began excavating, uncovering vertebrae, ribs, and limb bones, many of them still connected. Giddy with excitement, they called Antônio Celso de Arruda Campos, a paleontology professor in the nearby town of Monte Alto.
The fossils were recovered and taken to...