The Bauru Basin covers roughly 379,000 square kilometres, almost entirely within Brazil, with a few outcrops reaching into northeastern Paraguay. It is a sub-basin of the much older Paraná Basin, and everything in it was laid down on land. There is no ocean in this record — no marine limestone, no ammonites. Instead the strata read as a shifting inland world: wind-blown dune fields, shallow lakes, river channels that wandered and filled, alluvial fans building out from higher ground. Sandstone dominates, with beds of conglomerate, siltstone and mudstone between. The whole succession spans the Coniacian through the Maastrichtian stages, roughly 89 to 66 million years ago, which places its final chapters right at the end of the Cretaceous. This was interior Gondwana, dry and seasonal, in the long twilight of the dinosaurs.

Stratigraphers have argued about how to divide the Bauru Group, and the argument matters more than it sounds. In 1996 Fernandes and Coimbra split it into four formations: Adamantina, Uberaba, Araçatuba and Marília. Two years later Fernandes revised the scheme, breaking the sprawling Adamantina into three — Vale do Rio do Peixe, São José do Rio Preto and Presidente Prudente — for a total of six. Naming rock is how palaeontology keeps time. A fossil is only as informative as the unit it came from, so every reshuffle of these boundaries reshuffles which animals lived alongside which, and in what order. Recent work has continued the process, carving units such as the Serra da Galga Formation out of the sequence near Uberaba.

The 1945 discovery happened on Fazenda Cassú, near the old Mangabeira railway station north of Uberaba, in the district of Peirópolis. Price was invited to investigate and worked sites across the region until 1974 — three decades of quarrying in country where fossils tend to appear wherever the ground has been cut open. His name is now on the institution that grew from it. Uberaba began building the Llewellyn Ivor Price palaeontological research centre and the Museu dos Dinossauros at Peirópolis in 1991, about 25 kilometres from the city. Since 2010 the centre, the museum and the former national palaeontology network building have operated together as the Complexo Cultural e Científico de Peirópolis, run by the Federal University of the Triângulo Mineiro. Visitors can stand at the quarries themselves.

Two groups dominate the Bauru fauna, and only one of them is what most people expect. The sauropods are here in force — titanosaurs, the long-necked giants that were the last great sauropod lineage on Earth. Uberabatitan ribeiroi, estimated at up to 26 metres, is among the largest dinosaurs known from Brazil and stands assembled in the Peirópolis exhibitions; Baurutitan britoi came out of the same neighbourhood of rock. Theropods hunted them, abelisaurids among them. But the most diverse tetrapods in these beds are notosuchian crocodyliforms: crocodile relatives built for life on dry land, with long legs, deep skulls and, in some species, teeth shaped more like a mammal's than a reptile's. Fishes, frogs, turtles and lizards fill out an ecosystem that looks nothing like the swamp scenes usually painted for the Cretaceous.

Because the top of the group reaches into the Maastrichtian, the Bauru rocks carry Brazil's record of the final dinosaurs — the ones alive when the asteroid arrived. It is a record with quiet parts. Alongside the titanosaur vertebrae are the shells of snails and freshwater mussels, catalogued in a burst of work by Sérgio Mezzalira in 1974: Anodontites pricei, Diplodon arrudai, Sancticarolis tolentinoi, Florenceia peiropolensis, whose name points straight back to Peirópolis. A newer species, Physa mezzalirai, was described in 2011 and named for the man who described the rest. Those shells are the evidence that this dry interior still held standing water — ponds and slow channels where molluscs could live, in a landscape otherwise dominated by sand.