Romualdo Formation Explained

Romualdo Formation
Type:Geological formation
Age:Early Albian
~
Period:Aptian
Prilithology:Mudstone
Otherlithology:Limestone, shale
Region:Pernambuco, Piauí & Ceará
Coordinates:-7.2°N -39.3°W
Paleocoordinates:-12.2°N -10.7°W
Unitof:Santana Group
Underlies:Exu & Arajara Formations
Overlies:Crato & Ipubi Formations
Thickness:2-
Extent:Araripe Basin
Map:Araripe Basin map - formations and resources.jpg

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 Santana Formation, named after the village of Santana do Cariri, lies at the base of the Araripe Plateau. It was discovered by Johann Baptist von Spix in 1819. The strata were deposited during the Aptian stage of the Early Cretaceous in a lacustrine rift basin with shallow marine incursions of the proto-Atlantic. At that time, the South Atlantic was opening up in a long narrow shallow sea.

The Romualdo 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 invertebrates, and crocodylomorphs. Even dinosaurs are represented (Spinosauridae, Tyrannosauroidea, Compsognathidae). The unusual taphonomy of the site resulted in limestone accretions that formed nodules around dead organisms, preserving even soft parts of their anatomy. In preservation, the nodules are etched away with acid, and the fossils often prepared by the transfer technique.[1]

Local mining activities for cement and construction damage the sites. Trade in illegally collected fossils has sprung up from the decade of 1970, 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.[2]

In addition, the weathering of Romualdo 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 Romualdo Formation rocks.

Geology and dating

The Crato Formation was previously considered the lowest member of the then Santana Formation, but has been elevated to a formal formation. The Crato Formation is the product of a single phase, where complicated sequence of sediment strata reflect changeable conditions in the opening sea. The age of the Romualdo Formation, formerly known as the Romualdo Member of the Santana Formation, has been controversial, though most workers have agreed that it lies on or near the Aptian-Albian boundary, about 112 million years ago. Nevertheless, a Cenomanian age cannot be ruled out.[3] [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 Romualdo Formation, which is about 10 Ma younger.[3]

Fossil content

Archosaurs

Indeterminate remains of non-avian theropods, avialans, ornithischians, and possibly oviraptorosaurs have been found in Ceara state, Brazil. The oviraptorosaurian remains have been re-identified as megaraptoran fossils.[5]

Dinosaurs

Dinosaurs
Genus Species Presence Notes Images
Angaturama[6] A. limaiCearáSpinosauridae. Partial skull (rostralmost portion).[7] Possible junior synonym of Irritator challengeri.
Aratasaurus[8] A. museunacionaliCeará A coelurosaur. Partial right hindlimb.
Irritator[9] I. challengeriCearáSpinosauridae. Partial skull (posterior half); one of the most complete spinosaurid skulls known.
MirischiaM. asymmetricaPernambucoCompsognathidae. Pelvis and partial left hindlimb.
SantanaraptorS. placidusCearáA possible tyrannosauroid. Some caudal vertebrae, partial pelvis, most of both hindlimbs.[10]

Crocodylomorphs

Crocodylomorphs
Genus Species Presence Notes Images
AraripesuchusA. gomesiiRomualdo FormationType specimen 423-R is a single skull articulating with part of a lower jaw. A more complete specimen, AMNH 24450, is at the American Museum of Natural History.
CaririsuchusC. camposiRomualdo FormationA peirosaurid crocodyliform.

Pterosaurs

Pterosaurs
Genus Species Presence Images
Anhanguera
  • A. blittersdorffi
  • A. santanae
  • A. araripensis
  • A. robustus
  • A. piscator
  • A. spielbergi
AraripedactylusA. dehmi
AraripesaurusA. castilhoi
Barbosania[11] B. gracilirostris
BrasileodactylusB. araripensis
CearadactylusC. atrox
"C." ligabuei[12]
KariridracoK. dianae
MaaradactylusM. kellneri
Santanadactylus
  • S. brasilensis
  • ?S. pricei
  • S. spixi
TapejaraT. wellnhoferi
ThalassodromeusT. sethi
TropeognathusT. mesembrinus
Tupuxuara
  • T. deliradamus
  • T. leonardii
  • T. longicristatus
UnwindiaU. trigonus

Turtles

Turtles
Genus Species Presence Notes Images
SantanachelysS. gaffneyialign=center [13]
CearachelysC. placidoialign=center [14]
AraripemysA. barretoialign=center [15]
EuraxemysE. essweinialign=center [16]
BrasilemysB. josaialign=center [17]

Fish

See also

References

Bibliography

Further reading

Notes and References

  1. Maisey et al., 1991, pp. 99–103
  2. Gibney. Elizabeth. 2014-03-06. Brazil clamps down on illegal fossil trade. Nature. en. 507. 7490. 20. 10.1038/507020a. 24598620. 0028-0836. 2014Natur.507...20G. free.
  3. Martill et al., 2007
  4. Martill, 2007
  5. Aranciaga Rolando. Alexis M.. Brissón Egli. Federico. Sales. Marcos A.F.. Martinelli. Agustín G.. Canale. Juan I.. Ezcurra. Martín D.. 2018. A supposed Gondwanan oviraptorosaur from the Albian of Brazil represents the oldest South American megaraptoran. Cretaceous Research. en. 84. 107–119. 10.1016/j.cretres.2017.10.019. 2018CrRes..84..107A . 0195-6671. 11336/93821. free.
  6. Weishampel, 2004, pp. 563–570
  7. "Table 4.1," in Weishampel, et al. (2004). Page 73.
  8. Juliana Manso Sayão . Antônio Álamo Feitosa Saraiva . Arthur Souza Brum . Renan Alfredo Machado Bantim . Rafael Cesar Lima Pedroso de Andrade . Xin Cheng . Flaviana Jorge de Lima . Helder de Paula Silva . Alexander W. A. Kellner . 2020 . The first theropod dinosaur (Coelurosauria, Theropoda) from the base of the Romualdo Formation (Albian), Araripe Basin, Northeast Brazil . Scientific Reports . 10 . 1 . Article number 10892 . 10.1038/s41598-020-67822-9 . 32651406 . 7351750 . free . 2020NatSR..1010892S .
  9. Martill. D. M.. Cruickshank. A. R. I.. Frey. E.. Small. P. G.. Clarke. M.. 1996-02-01. A new crested maniraptoran dinosaur from the Santana Formation (Lower Cretaceous) of Brazil. Journal of the Geological Society. en. 153. 1. 5–8. 10.1144/gsjgs.153.1.0005. 0016-7649. 1996JGSoc.153....5M. 131339386.
  10. "Table 5.1," in Weishampel, et al. (2004). Page 114.
  11. Elgin & Frey, 2011
  12. Unwin . D. M. . 2002 . On the systematic relationships of Cearadactylus atrox, an enigmatic Early Cretaceous pterosaur from the Santana Formation of Brazil . Mitteilungen Museum für Naturkunde Berlin, Geowissenschaftlichen Reihe . 5 . 1 . 1239–263. 10.5194/fr-5-239-2002 . free . 2002FossR...5..239U .
  13. https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=90355 Santanachelys gaffneyi
  14. https://paleobiodb.org/classic/displayCollResults?collection_no=128568 Juazeiro do Norte
  15. https://paleobiodb.org/classic/displayCollResults?collection_no=128565 Araripemys barretoi type locality
  16. https://paleobiodb.org/classic/displayCollResults?collection_no=83306 Crato
  17. https://paleobiodb.org/classic/displayCollResults?collection_no=92290 Chapada do Araripe
  18. Custódio. M.A.. Guaglio, F.. Warren, L.V.. Simões, M.G.. Fürsich, F.T.. Perinotto, J.A.. Assine, M.L.. The transgressive-regressive cycle of the Romualdo Formation (Araripe Basin): Sedimentary archive of the Early Cretaceous marine ingression in the interior of Northeast Brazil. Sedimentary Geology. 2017. 359. 359. 1–15. 10.1016/j.sedgeo.2017.07.010. 2017SedG..359....1C. 11449/175030. free.
  19. https://paleobiodb.org/classic/displayCollResults?collection_no=133574 Casa de Pedra
  20. Fara et al., 2005, p.152
  21. https://paleobiodb.org/classic/displayCollResults?collection_no=28052 Buxéxé, Santana do Cariri
  22. http://palaeo.gly.bris.ac.uk/Palaeofiles/Lagerstatten/santana/FosCrd25.htm Enneles audax
  23. http://palaeo.gly.bris.ac.uk/Palaeofiles/Lagerstatten/santana/FosCrd6.htm Iemanja palma
  24. https://paleobiodb.org/classic/displayCollResults?collection_no=124310 Placidichthys type locality
  25. Maisey . John G. . 2000-04-01 . Continental break up and the distribution of fishes of Western Gondwana during the Early Cretaceous . Cretaceous Research . en . 21 . 2 . 281–314 . 10.1006/cres.1999.0195 . 2000CrRes..21..281M . 0195-6671.
  26. https://paleobiodb.org/classic/displayCollResults?collection_no=165422 Ze Gomes

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