Fish fossils in the area were noted in 1823. When they were first methodically published, in 1993, the Crato Formation limestones provided a new site for
pterosaurs, one that also preserved insects that fell into a brackish lagoon and semionotid fish preserved in
phosphatized nodules. The fossils are usually compacted and preserved in layers of limestone. Fossil
Odonata (
dragonflies) and damselflies are especially rich in the Crato lagerstätte: currently 384 specimens have been recovered, 264 adults and 120 larvae. Hemiptera (true bugs) and Orthoptera (grasshoppers and crickets) are also abundant in number of species and in number of specimens. There are also plant remains. Local mining activities for cement and construction damage the sites. Trade in illegally collected fossils has sprung up in the last decade, driven by the remarkable state of preservation and beauty of these fossils and amounting to a considerable local industry. An urgent preservation program is being called for by paleontologists. In addition, the
weathering of Crato and Santana Formation rocks has contributed
soil conditions unlike elsewhere in the region. The
Araripe manakin (
Antilophia bokermanni) is a very rare bird that was discovered only in the late 20th century; it is not known from anywhere outside the characteristic forest that grows on the
Chapada do Araripe soils formed ultimately from Crato and Santana Formation rocks.
Definition The Crato Formation has often historically been considered the lowest member of the Santana Formation (or, alternatively, the Araripina Formation) of the Araripe Group, later redefined as the
Romualdo Formation of the
Santana Group. The Crato Member is the product of a single phase, where complicated sequence of sediment
strata reflect changeable conditions in the opening sea. The age of this strata has been controversial, though most workers have agreed that it lies on or near the Aptian-Albian boundary, about 112 million years ago. The extent of the Crato unit and its relationship to the Romualdo Formation had long been ill-defined. It was not until a 2007 volume on the unit by Martill, Bechly and Loveridge that the Crato Formation was given a formal type locality, and was formally made a distinct formation separate from the Santana, which is about 10 Ma younger. == Fossil content ==