The Crato Formation is a geologic

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondar ...

of Early Cretaceous ( Aptian) age in northeastern

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

Araripe Basin The Araripe Basin () is a rift basin covering about ,Neto et al., 2013, p.1 in Ceará, Piauí and Pernambuco states of northeastern Brazil. It is bounded by the Patos and Pernambuco lineaments, and is situated east of the Parnaíba Basin, southwe ...

. It is an important

Lagerstätte A Lagerstätte (, from ''Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that exhibits extraordinary fossils with exceptional preservation—sometimes including preserved soft tissues. These f ...

(undisturbed fossil accumulation) for palaeontologists. The strata were laid down mostly during the Aptian

age Age or AGE may refer to: Time and its effects * Age, the amount of time someone or something has been alive or has existed ** East Asian age reckoning, an Asian system of marking age starting at 1 * Ageing or aging, the process of becoming older ...

, about 113 million years ago. It thought to have been deposited in a

semi-arid A semi-arid climate, semi-desert climate, or steppe climate is a dry climate sub-type. It is located on regions that receive precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi- ...

lacustrine A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much larger ...

wetland A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The p ...

environment.Ribeiro et al., 2021 The Crato Formation earns the designation of Lagerstätte due to an exceedingly well preserved and diverse

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

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 of

pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 ...

s, reptiles and amphibians, invertebrates (particularly insects), and plants. Even dinosaurs are represented: a new maniraptor was described in 1996. The unusual

taphonomy Taphonomy is the study of how organisms decay and become fossilized or preserved in the paleontological record. The term ''taphonomy'' (from Greek , 'burial' and , 'law') was introduced to paleontology in 1940 by Soviet scientist Ivan Efremov t ...

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

History

Araripe Basin - depositional environments and sequence stratigraphy

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

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. Fossil

Odonata Odonata is an order of flying insects that includes the dragonflies and damselflies. Members of the group first appeared during the Triassic, though members of their total group, Odonatoptera, first appeared in Late Carboniferous. The two com ...

(

dragonflies A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of true dragonfly are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threa ...

) 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 Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement) ...

of Crato and Santana Formation rocks has contributed

soil Soil, also commonly referred to as earth or dirt Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty. Common types of dirt include: * Debri ...

conditions unlike elsewhere in the region. The

Araripe manakin The Araripe manakin (''Antilophia bokermanni'') is a species of critically endangered bird from the family of manakins (Pipridae). It was discovered in 1996 and scientifically described in 1998. The species epithet commemorates Brazilian zoologi ...

(''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 The Chapada do Araripe, also known as the Serra do Araripe, is a ''chapada'' ( plateau) in northeastern Brazil. The chapada forms the boundary of Ceará and Pernambuco states, and forms the watershed between the Jaguaribe River of Ceará, which fl ...

soils formed ultimately from Crato and Santana Formation rocks.

Definition

Araripe Basin - lake level cycles - Crato, Ipubi and Romualdo Formations

The Crato Formation has often historically been considered the lowest member of the Santana Formation (or, alternatively, the Araripina Formation) of the Araripe Group,Scherer et al., 2013, p.28 later redefined as the

Romualdo Formation 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 geological formation, previously designated as the Romualdo Member of the Sa ...

of the

Santana Group The Santana Group is a geologic group, formerly included as the middle part of the Araripe Group, in the Araripe Basin of northeastern Brazil. The group comprises the Crato, Ipubi and Romualdo Formations and is dated to the Aptian to Albian stag ...

.Assine, 1992, p.291Fabin et al., 2018, p.2050 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.Martill et al., 2007 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. The Crato Formation is considered time equivalent with the Paracuru Formation.Leite da Silva, 2003

Fossil content

Insects

(Note: Many more insects have been described than are present in the table below)

Arachnids

Fish

Amphibians

Squamata

Dinosaurs

Crocodylomorphs

Pterosaurs

Flora

Other fossils

* '' Araripenaeus timidus''Pinheiro, 2014, p.4 * †'' Cratoalloneura'' ** †'' Cratoalloneura acuminata'' ** †'' Cratoalloneura verdandia'' * †'' Cratoatractocerus'' ** †'' Cratoatractocerus grimaldii'' * †'' Cratoborellia'' ** †'' Cratoborellia gorbi'' * †'' Cratochrysa'' ** †'' Cratochrysa martinsnetoi'' ** †'' Cratochrysa sublapsa'' ** †'' Cratochrysa willmanni'' * †'' Cratocora'' ** †'' Cratocora crassa'' * †'' Cratocordulia'' ** †'' Cratocordulia borschukewitzi'' * †'' Cratocoris'' ** †'' Cratocoris shevchenkoae'' * †'' Cratocorydalopsis'' ** †'' Cratocorydalopsis brasiliensis'' * †'' Cratocossus'' ** †'' Cratocossus magnus'' * †'' Cratodactylus'' ** †'' Cratodactylus ferreirai'' ** †'' Cratodactylus kellneri'' * †'' Cratoelcana'' ** †'' Cratoelcana damianii'' ** †'' Cratoelcana zessini'' * †'' Cratoenigma'' ** †'' Cratoenigma articulata'' * †'' Cratogomphus'' ** †'' Cratogomphus erraticus'' * †'' Cratogryllus'' ** †'' Cratogryllus cigueli'' ** †'' Cratogryllus guimaraesae'' ** †'' Cratogryllus pentagonalis'' * †'' Cratohagenius'' ** †'' Cratohagenius erichweberi'' * †'' Cratohaglopsis'' ** †'' Cratohaglopsis santanaensis'' * †'' Cratohexagenites'' ** †'' Cratohexagenites longicercus'' ** †'' Cratohexagenites minor'' * †'' Cratokalotermes'' ** †'' Cratokalotermes santanensis'' * †'' Cratolindenia'' ** †'' Cratolindenia knuepfae'' * †'' Cratolocustopsis'' ** †'' Cratolocustopsis araripensis'' ** †'' Cratolocustopsis contumax’'' – type locality for species ** †'' Cratolocustopsis cretacea'' * †'' Cratomacer'' ** †'' Cratomacer ephippiger'' ** †'' Cratomacer immersus'' * †'' Cratomastotermes'' ** †'' Cratomastotermes wolfschwenningeri'' * †'' Cratomyia'' ** †'' Cratomyia cretacica'' ** †'' Cratomyia macrorrhyncha'' * †'' Cratonemonyx'' ** †'' Cratonemonyx martinsnetoi'' * †'' Cratonemopteryx'' ** †'' Cratonemopteryx audax'' ** †'' Cratonemopteryx robusta'' ** †'' Cratonemopteryx speciosa'' * †'' Cratonepa'' ** †'' Cratonepa enigmatica'' * †'' Cratonerthra'' ** †'' Cratonerthra corinthiana'' ** †'' Cratonerthra estevezae'' * †'' Cratoneura'' ** †'' Cratoneura dividens'' ** †'' Cratoneura longissima'' ** †'' Cratoneura pulchella'' * †'' Cratonympha'' ** †'' Cratonympha microcelata'' * †'' Cratopelocoris'' ** †'' Cratopelocoris carpinteroi'' * †'' Cratopetalia'' ** †'' Cratopetalia whiteheadi'' * †'' Cratopetalura'' ** †'' Cratopetalura petruleviciusi'' ** †'' Cratopetalura petruleviciusi'' * †'' Cratopsychopsis'' ** †'' Cratopsychopsis maiseyi'' * †'' Cratopteryx'' ** †'' Cratopteryx nemopteroides'' ** †'' Cratopteryx robertosantosi'' * †'' Cratoraricrus'' ** †'' Cratoraricrus oberlii'' * †'' Cratoscalapha'' ** †'' Cratoscalapha electroneura'' * †'' Cratosirex'' ** †'' Cratosirex sennlaubi'' * †'' Cratosisyrops'' ** †'' Cratosisyrops gonzagai'' * †'' Cratosmylus'' ** †'' Cratosmylus magnificus'' * †'' Cratostenophlebia'' ** †'' Cratostenophlebia schwickerti'' * †'' Cratotabanus'' ** †'' Cratotabanus stonemyomorphus'' * †'' Cratotetraspinus'' ** †'' Cratotetraspinus fossorius'' * †'' Cratotipula'' ** †'' Cratotipula latialata'' * †'' Cratovitisma'' ** †'' Cratovitisma oldreadi'' * †'' Cratovoluptia'' ** †'' Cratovoluptia criptoneura'' * †'' Cratozeunerella'' ** †'' Cratozeunerella amedegnatoi'' ** †'' Cratozeunerella godoii'' ** †'' Cratozeunerella neotropica'' ** †'' Cratozeunerella nervosa'' ** †'' Cratozeunerella soaresi'' ** †'' Cratozeunerella titanella''

References

Bibliography

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