Nothing about this should have worked. A footprint is a hole in soft ground, and soft ground does not last. What made the Rio do Peixe basin exceptional was the rhythm of its Early Cretaceous climate, which happened to be almost exactly the rhythm the sertão keeps today. Animals walked the damp margins of ponds and rivers during the rains. Then the drought came, and the mud baked hard enough to hold its shape. Then floods returned and buried the hardened surface under fresh sand and clay, sealing it before anything could erase it. Repeat that cycle for long enough and you get what the Sousa Formation actually contains: not one trampled surface but roughly twenty stacked stratigraphic levels, each recording a different afternoon in the Berriasian to Hauterivian, at least 143 million years ago.

The valley takes in the city of Sousa and ten other municipalities, and tracks turn up at about thirty separate localities within it. Palaeontologists have logged over fifty distinct types of trace and footprints attributed to more than eighty species, among them stegosaurids, allosauroids and iguanodonts. Most of the makers were carnivores. The size range is the part that lands hardest in person: the smallest prints measure about five centimetres, left by animals no bigger than a chicken, while the largest run to forty centimetres, the stride of a four-tonne iguanodont. Some of the ichnogenera named from these beds exist nowhere else — Sousaichnium, described by the palaeontologist Giuseppe Leonardi in 1979, and Moraesichnium, which carries the name of the engineer who first drew the tracks properly.

A local farmer, Anísio Fausto Silva, noticed the marks in the late nineteenth century. He was not looking for fossils; nobody in Brazil was, and when the first dinosaur footprints in the country were recognised here in 1897, there was no Brazilian palaeontology to receive them. The man who took them seriously was Luciano Jacques de Moraes, an engineer rather than a specialist, who studied the site in the early twentieth century and published careful descriptions and drawings in his 1924 book Serras e Montanhas do Nordeste. His drawings did what drawings do best in a place that floods annually — they preserved the evidence independently of the stone. Formal protection took considerably longer. The Área de Relevante Interesse Ecológico Vale dos Dinossauros, 145.79 hectares administered by the Chico Mendes Institute for Biodiversity Conservation, was created on 18 December 1984; the municipality of Sousa added a smaller, fully protected Natural Monument of about 40 hectares in 2002.

Visiting the site means walking above it. A R$1.3 million renovation funded by the federal government and Petrobras reopened the attraction on 24 May 2013, having rebuilt the museum, the exhibition space, the auditorium and the paths, and brought the lookout gazebos up to accessibility standards. The suspended walkways were the point: they carry visitors over fifty fossilised prints of noasaurid carnivores and fifty-three left by iguanodonts without anyone setting foot on the surface. There had also been proposals to divert the Peixe River itself, which floods the tracks every wet season — a permanent fix that would trade the site's greatest hazard for a heavily engineered landscape.

Protection on paper and protection in practice are different things. In December 2015 reporters found the valley in visible decline: renovation work suspended after funding to the contractor stalled, access roads swallowed by scrub, heaps of sand and loose cobblestones around the entrance, and the replica Tyrannosaurus destroyed. The Federal Public Ministry in Sousa responded in February 2016 by recommending that SUDEMA, the Paraíba environment agency, produce a management plan for the natural monument within ninety days, spelling out how the site's integrity would be secured and how it would be woven into the economic life of the surrounding communities. The MPF also asked for a report within thirty days on what the Sousa prefecture had actually been doing there, warning that anything beyond protection of the unit should be halted. It is a familiar bind for the Brazilian interior: a site of genuine international importance, in a municipality without the budget to match it.