The Romualdo Formation is a geologic Konservat-Lagerstätte in northeastern Brazil's Araripe Basin where the states of Pernambuco, Piauí and Ceará come together.

The strata were deposited during the Aptian stage of the Early Cretaceous in a lacustrine rift basin with shallow marine incursions of the proto-Atlantic.

The Romualdo Formation earns the designation of Lagerstätte due to an exceedingly well preserved and diverse fossil faunal assemblage.

The unusual taphonomy of the site resulted in limestone accretions that formed nodules around dead organisms, preserving even soft parts of their anatomy.

The Crato Formation is the product of a single phase, where complicated sequence of sediment strata reflect changeable conditions in the opening sea.