Santana Formation, Geological formation in Pernambuco, Brazil

The Santana Formation is a geological layer in the Araripe Basin of northeastern Brazil composed of horizontal limestone beds mixed with clay, silt, and sand layers. These strata contain abundant fossilized remains of pterosaurs, fish, insects, and plants from the Early Cretaceous period.

The first fossils were found in 1819 by Bavarian researchers Johann Baptist von Spix and Carl Friedrich Philipp von Martius, who came upon well-preserved fish while exploring the then-unstudied region. News of the find reached paleontologists worldwide. The first pterosaur, Araripesaurus castilhoi, was described by Llewellyn Ivor Price in 1971. The unit was long treated as the Romualdo Member of the Santana Formation and was only formally separated from the older Crato Formation in a 2007 volume by Martill, Bechly and Loveridge.

The name Santana comes from the village of Santana do Cariri, not from a settler. Since the 1970s, illegal fossil collecting has grown into a local trade, driven by the preservation of the specimens. The Araripe manakin, a rare bird discovered in the late 20th century, lives only in the forest on soils formed from Romualdo Formation rocks.

The fossil-bearing strata lie at the foot of the Araripe Plateau, where the borders of Pernambuco, Piauí and Ceará meet, near Santana do Cariri. There is no public excavation site to tour; the layers are quarried for cement and construction, and illegally collected fossils feed a trade dating from the 1970s. Paleontologists call for an urgent preservation program, so access to exposures should be arranged through researchers or local institutions rather than attempted independently.

The limestone nodules formed around dead organisms preserved soft tissues with exceptional clarity, allowing scientists to examine gut contents and organ details. This reveals ancient feeding patterns and predator-prey interactions that fossils elsewhere rarely show.