stratigraphic units: Crato Formation that is composed of six intervals of laminated limestones (C1 to C6), interbedded with calciferous siltstones and marls, and is very rich in fossils of vertebrate and invertebrate organisms Ipubi Formation, that is mainly composed of organic-rich, black greenish bituminous shales, claystones and algal limestones that are interbedded with gypsum-anhydrite beds Romualdo Formation, that represents a calciferous siliciclastic succession composed of fine to medium-grained sandstones, argillaceous siltstones, calciferous shales, and limestones, very rich in fossils. This formation recorded the marine proto-Atlantic incursion that involved the Araripe Basin, and other interior basins and created a large seaway throughout the Borborema Province during the Albian 5) Post-rift II phase - Albian to Cenomanian - characterized by a major sag phase, and is formed by two stratigraphic units: Araripina Formation, that occurs in the western region of the basin and is composed by rhythmites and heterolithic layers of reddish, purplish and yellowish fine-grained sandstone and mudstone Exu Formation, that comprises medium-to coarse grained sandstones, fine grained clayey sandstones and local conglomeratic beds Fossil content The upper and lower formations of the group are highly fossiliferous, with mainly insects, amphibians, fish, and flora dominating the lower Crato Formation, shrimps (Araripenaeus timidus), and various genera of dinosaurs and fish in the Romualdo Formation. A rich assemblage of pterosaur fossils are found in both formations, and the Ipubi Formation provided an indeterminate Pelomedusoides turtle. The Santana Group provided several feathers of birds, among those the first record of Mesozoic birds in Brazil. Gallery See also Chapada do Araripe Ariri Formation Guarujá Formation Itapecuru Formation References Bibliography Further reading Geologic groups of South America Geologic formations of Brazil Lower Cretaceous Series of South America Cretaceous Brazil Albian Stage Aptian Stage Shale formations Sandstone formations Mudstone formations Siltstone formations Marl formations Limestone formations Evaporite deposits Lacustrine deposits Shallow marine deposits Landforms of Ceará Landforms of Pernambuco Landforms of Piauí Northeast Region, Brazil