The Crato Formation is a geologic formation of

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

(

Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...

) age in northeastern

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

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, south ...

. It is an important

Lagerstätte A Fossil-Lagerstätte (, from ''Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that preserves an exceptionally high amount of palaeontological information. ''Konzentrat-Lagerstätten'' preserv ...

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

age Age or AGE may refer to: Time and its effects * Age, the amount of time someone has been alive or something 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 aridity, dry climate sub-type. It is located on regions that receive precipitation below Evapotranspiration#Potential evapotranspiration, potential evapotranspiration, but not as l ...

lacustrine

wetland A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor ( anoxic) processes taking place, especially ...

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 preserve ...

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 are 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 million to 66 million years ago). Pterosaurs are the earli ...

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 language, Greek , 'burial' and , 'law') was introduced to paleontology in 1940 by Soviet scientis ...

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 predatory flying insects that includes the dragonflies and damselflies (as well as the '' Epiophlebia'' damsel-dragonflies). The two major groups are distinguished with dragonflies (Anisoptera) usually being bulkier with ...

(

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

) 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, sunlight, and biological organisms. It occurs '' in situ'' (on-site, with little or no move ...

of Crato and Santana Formation rocks has contributed

soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

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,Scherer et al., 2013, p. 28. Retrieved 2018-10-05. later redefined as the

Romualdo Formation The Romualdo Formation is a geologic Lagerstätte, 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 Mem ...

of the Santana Group.Assine, 1992, p. 291. Retrieved 2018-10-05.Fabin et al., 2018, p. 2050. Retrieved 2018-10-05. The Crato Member is the product of a single phase, where complicated sequence of sediment

strata In geology and related fields, a stratum (: strata) is a layer of Rock (geology), rock or sediment characterized by certain Lithology, lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by v ...

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. Retrieved 2018-10-06. 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. Retrieved 2018-10-06.

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. Retrieved 2018-10-06. * †'' 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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