The Santana Formation is one of the most important fossil sites in the world. It is located in the region Santana in eastern Brazil in Araripe Basin on the border of the states of Pernambuco, Piauí and Ceará. The excavation site is located at the foot of Araripe Plateau, the highest elevation in the Araripe Basin with a maximum height of 600 to 900 meters and an area of about 200 kilometers from east to west. The fossils from the Santana Formation are from the early Cretaceous period, about 110 million years ago.
The first fossils of the formation were discovered in 1819 by the two researchers Bavarian Johann Baptist von Spix and Carl Friedrich Philipp von Martius as they explored this time still completely unexplored region while came across very well-preserved fossils of fish. The news of this discovery was spread very quickly, and thus came to paleontologists around the world. The first pterosaur ( Araripesaurus castilhoi ) was in 1971 by Llewellyn Ivor Price ( 1905-1980 ) described scientifically.
Geology of the Araripe Basin
The Santana Formation formed during the Cretaceous before about 90 to 110 million years. At this time there came to the breakup of the giant continent of Gondwana and the two parts of South America and Africa away from each other. Accordingly, the living conditions changed the time of deposition time and space quickly, which is reflected in the sediments of the Santana Formation.
The sedimentary rocks are positioned on a granite base of Proterozoic metamorphic rocks, mainly gneiss, and volcanic rocks. With the Cariri lineup as the lowest layer member, which consists mainly of sandstone and gravel, uses the sequence. This is followed by the Missao -Velha lineup with red and green sandstone ( mudstone ) and the Crato Formation, where the sandstone has a very high content of organic material and is interlinked with Solnhofen. The next layer, the Ipubi lineup consists of Evaporitgesteinen, which are salt rocks, which are among the chemical sediments. It follows the existing mainly of fine sand and gravel Batateiras lineup.
Composed of thin-plate limestones Crato member is the older of the fossiliferous layer limbs. It mainly contains fossils of terrestrial arthropods and plants. The actual Santana Formation ( Romualdo also layer element) with the known fish fossils lies about it and basically again from fine-grained sandstone with well-trained fossil horizons, mostly in hard calcareous nodules. The conclusion of the layer sequence forms which characterized by further sandstones, coarse sand and gravel Exu Formation ( nomenclature according to Martill, 1993).
Fossils of the Santana Formation
The Santana Formation mainly contains fossils of various fish species of the early Cretaceous period. There are also Santana fossils also of different amphibians, reptiles ( about crocodiles and turtles), pterodactyls ( Ornithocheirus and Tapejara ) and dinosaurs. Even insects, scorpions, spiders and flowering plants and ferns were found in remarkable quality. The good preservation of fossils and the level of detail is mainly due to the rapid sedimentation and the fine grain of the substrate.
Particularly well-known, rich and important are the fossils of fish. This includes many types of bony fish, but also sharks and rays, and coelacanths. Many of these fish were only discovered here, some (such as the sprat -like Dastilbe crandalli ) also on the east coast of the African continent, which they are cited as evidence for Gondwana theory.
Pterosaurs from the Santana Formation:
- Anhangueridae Anhanguera santanae
- Anhanguera blittersdorffi
- Anhanguera piscator
- Tupuxuara longicristatus
- Tupuxuara leonardi
- Cearadactylus atrox
- Santanadactylus spixi
- Araripesaurus castilhoi
- Brasileodactylus araripensis
- Coloborhynchus araripensis
- Coloborhynchus robustus
- Criorhynchus mesembrinus
- Tapejara wellnhoferi
- Tapejara imperator
- Arthurdactylus conandoylei
- Thalassodromeus sethi
- Ludodactylus sibbicki
- Unwindia trigonus
For pterosaurs, the formation a particularly rich reference dar. In no other place in the world were discovered here as so many different pterosaurs of the Cretaceous. It copies were discovered almost all known at the time pterosaur groups, some taxa are known only by even these specimens.
Among the dinosaurs, it is mainly theropods, which were discovered in the Santana Formation; such as the Santanaraptor discovered in 1999 and the Spinosauriden Angaturama limai and Irritator challengeri, however, represent a very high probability fossils of the same species and thus synonyms.
Noteworthy are also the finding of the turtles in this place, about the oldest known sea turtle Santanachelys gaffneyi and Araripemydidae Araripemys barretoi and Bothremydidae Cearachelys placidoi.
The discoveries of well-preserved arthropods such as spiders, scorpions and insects ( dragonflies, Fly, cicadas and others) go into the thousands, as well as the footprints of flowering plants and ferns.
The Santana Formation was very likely due to the sedimentation of a shallow inland sea, which was filled with fresh or brackish water. Regarding the salinity prevails mainly due to the fossil record so far no agreement, speak some fish for a salt-free or low-salt water, others for salt water. The insects discoveries are rather is an index for freshwater, the discovery of the Santanachelys gaffneyi turn suggests salt water. Therefore, the greatest recognition is the theory that it was a brackish lagoon, which was consistent with the sea in conjunction. The climate was tropical and warm to the current climate in Brazil have largely complied with.