- Santana Formation
__NOTOC__The Santana Formation is a geologic Lagerstätte (undisturbed fossil accumulation) in northeastern
Brazil 's Araripe Basin where the states ofPernambuco ,Piauí andCeará come together. The geological formation, named after the village of Santana do Cariri, lies at the base of the Araripe Plateau. The strata were laid down during the earlyCretaceous , specifically during the lateAptian toCenomanian , 108 to 92 million years ago, in a shallow inland sea. At that time, the South Atlantic was opening up in a long narrow shallow sea.The Santana Formation earns the designation of Lagerstätte due to an exceedingly well preserved and diverse
fossil faunal assemblage. Some 25 species of fossil fishes are often found with stomach contents preserved, enabling paleontologists to study predator-prey relationships in this ecosystem. There are also fine examples ofpterosaur s, reptiles and amphibians, invertebrates (particularly insects), and plants. Even dinosaurs are represented: a new maniraptor was described in 1996. The unusualtaphonomy of the site resulted in limestone accretions that formed nodules around dead organisms, preserving even soft parts of their anatomy.The Crato Member is the product of a single phase in the Santana Formation, where complicated sequence of sediment strata reflect changeable conditions in the opening sea.
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 forpterosaur s, 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. FossilOdonata (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 Santana Formation rocks has contributedsoil conditions unlike elsewhere in the region. TheAraripe 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 theChapada do Araripe soils formed ultimately from Santana Formation rocks.Notable taxa
Dinosaurs
Theropoda :Spinosauroidea ::Spinosauridae :::"Angaturama ":::"Irritator "Insects
Hemiptera Neuropterida "incertae sedis ":"Rafaelia "Odonata Orthoptera Pterosaurs
Turtles
Cryptodira :Protostegidae ::"Santanachelys "See also
*
List of fossil sites "(with link directory)"
*List of dinosaur-bearing rock formations External links
* [http://palaeo.gly.bris.ac.uk/Palaeofiles/Lagerstatten/santana/ Santana Formation fossils]
* [http://www.ingentaconnect.com/content/ geol/jgs/1996/00000153/00000001/15310005 "A new crested maniraptoran dinosaur from the Santana Formation"]
* [http://www.amnh.org/exhibitions/expeditions/treasure_fossil/Treasures/Brasilian_Fossil_Fish/brasil.html?50 American Museum of Natural History:] Brazilian fossil fishes
* [http://www.unb.br/ig/sigep/sitio005/sitio005english.htm Maria Somália Sales Viana and Virgínio Henrique Lopes Neumann, "The Crato Member of the Santana Formation, Ceará State" ]Further reading
*David A. Grimaldi (ed.) 1990. "Insects from the Santana Formation, Lower Cretaceous, of Brazil", Bulletin of the American Museum of Natural History no. 195
*John G. Maisey (ed.) 1991. "Santana Fossils - An Illustrated Atlas" (T.H.F. Publ.)
*David M. Martill, 1993. "Fossils of the Santana and Crato Formations, Brazil" (Field Guide to Fossils no. 5) (The Palaeontological Association) ISBN 0-901702-46-3
*David M. Martill, Günter Bechly and Robert F. Loverridge (eds) 2007. "The Crato Fossil Beds of Brazil: Window into an Ancient World" (Cambridge University Press) ISBN 978-0-521-85867-0
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