Qualla: Santana Group

Santana Group: Introduction

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit Fabin et al., 2018, CC BY 4.0. A hundred and thirteen million years ago, northeastern Brazil was a rift. South America and Africa were pulling apart. Where the town of Crato now sits, a chain of shallow lakes and lagoons filled the rift basin, and the creatures that died in those lakes sank through still, oxygen-poor water into fine mud. That mud became limestone, and that limestone preserved whatever fell into it with astonishing fidelity: fish with soft tissue, pterosaurs with wing membranes, dinosaurs with skin impressions, insects with patterned wings, and feathers so detailed that scientists can see individual barbs. The Santana Group, dated to the Early Cretaceous, is one of the richest fossil deposits on Earth.

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Image: Fabin et al., 2018 | CC BY 4.0

Santana Group: Three Formations, One Story

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit Fabin et al., 2018, CC BY 4.0. The Santana Group stacks three rock formations on top of each other, each telling a different chapter of the same basin. The Crato Formation sits at the bottom, laid down as six intervals of laminated limestone with calcareous siltstone and marl between them. It holds most of the...

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Image: Fabin et al., 2018 | CC BY 4.0

Santana Group: Feathers Before the Birds

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit Prado et al., 2016, CC BY-SA 4.0. The Santana Group holds the first record of Mesozoic birds from Brazil. Fossil feathers found in the Crato and Romualdo formations show that feathered animals were already living in the basin at a time when the lineages leading to modern birds were still diverging from their ther...

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Image: Prado et al., 2016 | CC BY-SA 4.0

Santana Group: The Pterosaur with the Headcrest

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit Fabin et al., 2018, CC BY 4.0. Thalassodromeus sethi, named in 2002, was a large pterosaur recovered from the Romualdo Formation. Its lower jaw and the base of its skull preserve a bony crest that rose almost vertically above its head, taller than the rest of its body depending on how the angle of the neck is ...

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Image: Fabin et al., 2018 | CC BY 4.0

Santana Group: Why the Fossils Are So Good

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit Carlos E. Fabin, Osvaldo J. Correia Filho, Márcio L. Alencar, José A. Barbosa, Tiago S. De Miranda, Virgínio H. Neumann, Igor F. Gomes, Felipe R. De Santana, CC BY 4.0. Most places on Earth do not preserve soft tissue. Bodies rot, bones disarticulate, scavengers take what they can. The Santana Group preserves fossils the way it does because the conditions at the bottom of the basin's lakes were rare and repeatable. The water was stratified, with...

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Image: Carlos E. Fabin, Osvaldo J. Correia Filho, Márcio L. Alencar, José A. Barbosa, Tiago S. De Miranda, Virgínio H. Neumann, Igor F. Gomes, Felipe R. De Santana | CC BY 4.0

Santana Group: The Basin's Deep History

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit Fabin et al., 2018, CC BY 4.0. The rocks of the Santana Group are only the middle of a much longer basin story. Before the rift, the area was quiet and stable, with Silurian and Devonian sandstones from braided rivers. In the Late Jurassic came a pre-rift phase, where slow thermal subsidence laid down red shal...

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Image: Fabin et al., 2018 | CC BY 4.0