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The Crato Formation is a geologic formation of Early Cretaceous (Aptian) age in northeastern Brazil's Araripe Basin. It is an important Lagerstätte (undisturbed fossil accumulation) for palaeontologists. The strata were laid down mostly during the early Aptian age, about 113 million years ago, in a shallow inland sea. At that time, the South Atlantic was opening up in a long narrow shallow sea.

Crato Formation
Stratigraphic range: Latest Aptian
~115–113 Ma
TypeGeological formation
Unit ofSantana Group
Sub-unitsNova Olinda Member
UnderliesRomualdo & Ipubi Formations
OverliesBarbalha Formation
Lithology
PrimaryMudstone, limestone
OtherSiltstone
Location
Coordinates7°06′S 39°42′W / 7.1°S 39.7°W / -7.1; -39.7Coordinates: 7°06′S 39°42′W / 7.1°S 39.7°W / -7.1; -39.7
Approximate paleocoordinates8°36′S 8°00′W / 8.6°S 8.0°W / -8.6; -8.0
RegionCeará, Pernambuco
Country Brazil
ExtentAraripe Basin
Type section
Named forCrato, Ceará
Araripe Basin map - formations and resources.jpg
Extent of the Santana Group, to which the Crato Formation belongs, in blue

The Crato 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 of pterosaurs, reptiles and amphibians, invertebrates (particularly insects), and plants. Even dinosaurs are represented: a new maniraptor was described in 1996. The unusual taphonomy of the site resulted in limestone accretions that formed nodules around dead organisms, preserving even soft parts of their anatomy.

HistoryEdit

 
Schematic development of the depositional environments of the Santana Group

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 pterosaurs, 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 (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 Crato and Santana Formation rocks has contributed soil 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.

DefinitionEdit

 
Lake level cyclicity in the Santana Group

The Crato Formation has often historically been considered the lowest member of the Santana Formation (or, alternatively, the Araripina Formation) of the Araripe Group,[1] later redefined as the Romualdo Formation of the Santana Group.[2][3] 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.[4]

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.[4] The Crato Formation is considered time equivalent with the Paracuru Formation.[5]

Fossil contentEdit

InsectsEdit

Insects of the Crato Formation
Genus Species Presence Description Images

Araripenymphes[6]

A. seldoni

Nova Olinda Member

A Nymphid lacewing

Gracilepteryx

G. pulchra

A Eolepidopterigidae moth

Makarkinia[7]

M. adamsi
M. kerneri

A Kalligrammatid lacewing

Mickoleitia

M. longimanus

A Coxoplectopteran insect

Netoxena

N. nana

A Eolepidopterigidae moth

Principiala[8]

P. incerta

An Ithonidae lacewing, type species of Principiala

Psamateia

P. calipsa

A Eolepidopterigidae moth

Rafaelia

R. maxima

Neuropterida incertae sedis

Undopterix

U. cariensis

An Eolepidopterigidae moth

ArthropodsEdit

Arthropods of the Crato Formation
Genus Species Presence Description Images
Protoischnurus P. axelrodorum Scorpion

FishEdit

Fish of the Crato Formation
Genus Species Presence Description Images Notes
Araripelepidotes Araripelepidotes temnurus
Belonostomus Belonostomus sp.
Calamopleurus Calamopleurus cylindricus
Cladocyclus Cladocyclus gardneri An Ichthyodectidae fish
Cratoamia Cratoamia gondwanica
Dastilbe Dastilbe crandalli
Lepidotes Lepidotes wenzae
Placidichthys Placidichthys bidorsalis
Santanichthys Santanichthys diasii

AmphibiansEdit

Amphibians of the Crato Formation
Genus Species Presence Description Images

Arariphrynus[18]

Arariphrynus placidoi[18]

Cratia[18]

Cratia gracilis[18]

Eurycephalella[18]

Eurycephalella alcinae[18]

Pipoidea[18]

Possible indeterminate pipoid remains.[18]

SquamataEdit

Squamatans of the Crato Formation
Genus Species Presence Description Images

Calanguban

C. alamoi

A non-iguana lizard

Tetrapodophis

T. amplectus

A stem group snake with limbs

DinosauriaEdit

Dinosaurs and birds of the Crato Formation
Genus Species Presence Notes Images

?Avialae

?Avialan species

Numerous isolated feathers

Cratoavis

C. cearensis

Enantiornithine

 
Reconstruction of Cratoavis and Mirischia

?Spinosauroidea

?Spinosaur species

Isolated tooth

CrurotarsansEdit

Crocodylomorphs of the Crato Formation
Genus Species Presence Description Images

Susisuchus

Susisuchus anatoceps[19]

cf. Susisuchus sp.[20]

Undescribed species

PterosaursEdit

Pterosaurs of the Crato Formation
Genus Species Presence Description Images

Arthurdactylus

A. conandoylei

Aymberedactylus

A. cearensis

A basal member of the Tapejarinae.

Brasileodactylus

B. sp.

Lacusovagus

L. magnificens

Nova Olinda Member

Ludodactylus

L. sibbicki

An ornithocheirid

Tupandactylus

T. imperator
T. navigans

?Tupuxuara

?T. sp.

FloraEdit

Flora of the Crato Formation
Species Notes
Araucaria cartellei, Brachyphyllum obesum, B. castilhoi, B. insigne, Iara iguassu, Caytoniales sp., Ephedra sp., Araripia florifera, Araucarites vulcanoi, Cariria orbiculiconiformis, Cearania heterophylla, Cratonia cotyledon, Endressinia brasiliana,Klitzchophyllites flabellatus, Novaolindia dubia, Pluricarpellatia peltata, Podozamites lanceolatus, Protananas lucenae, Ruffordia goeppertii, Tomaxellia biforme, Welwitschiaprisca austroamericana, Welwitschiophyllum brasiliense, Welwitschiostrobus murili, Araucariostrobus sp., Frenelopsis sp., Isoetites sp., Lindleycladus sp., Schizoneura sp.

Other fossilsEdit

See alsoEdit

ReferencesEdit

  1. ^ Scherer et al., 2013, p.28
  2. ^ Assine, 1992, p.291
  3. ^ Fabin et al., 2018, p.2050
  4. ^ a b Martill et al., 2007
  5. ^ Leite da Silva, 2003
  6. ^ Myskowiak, 2016
  7. ^ Bechly et al., 2016
  8. ^ Makarkin & Menon, 2007
  9. ^ Aparecida et al., 2015, p.25
  10. ^ Aparecida et al., 2015, p.35
  11. ^ Aparecida et al., 2015, p.29
  12. ^ Aparecida et al., 2015, p.36
  13. ^ Aparecida et al., 2015, p.31
  14. ^ Aparecida et al., 2015, p.51
  15. ^ Aparecida et al., 2015, p.26
  16. ^ Aparecida et al., 2015, p.33
  17. ^ Aparecida et al., 2015, p.47
  18. ^ a b c d e f g h Báez et al., 2009
  19. ^ Salisbury et al., 2003
  20. ^ Figueiredo & Kellner, 2009
  21. ^ Jorge de Lima et al., 2015, p.102
  22. ^ Pinheiro, 2014, p.4

BibliographyEdit

Further readingEdit