// Workers AI · dad joke modeWhat did the Romualdo Formation say? "I'm a rock-solid formation.

Romualdo Formation
Romualdo Formation
Stratigraphic range: Early Albian; ~111–108 Ma PreꞒ Ꞓ O S D C P T J K Pg N B V H B Apt. Albian C T C S Cam. M
	Fossils of Anhanguera (top) and Santanadactylus (bottom) from the Romualdo Formation
Type	Geological formation
Unit of	Santana Group
Underlies	Exu & Arajara Formations
Overlies	Crato & Ipubi Formations
Thickness	2–10 m (6.6–32.8 ft)
Lithology
Primary	Mudstone
Other	Limestone, shale
Location
Coordinates	7°12′S 39°18′W / 7.2°S 39.3°W
Approximate paleocoordinates	12°12′S 10°42′W / 12.2°S 10.7°W
Region	Pernambuco, Piauí & Ceará
Country	Brazil
Extent	Araripe Basin
	Romualdo Formation (Brazil)

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

Color key

Taxon	Reclassified taxon	Taxon falsely reported as present	Dubious taxon or junior synonym	Ichnotaxon	Ootaxon	Morphotaxon

Notes
Uncertain or tentative taxa are in small text; ~~crossed out~~ taxa are discredited.

Archosaurs

Indeterminate remains of non-avian theropods, avialans, ornithischians, and possibly oviraptorosaurs have been found in Ceara state, Brazil.^[5] The oviraptorosaurian remains have been re-identified as megaraptoran fossils.^[6]

Dinosaurs

Dinosaurs of the Romualdo Formation
Genus	Species	Presence	Materials	Notes	Images
Angaturama^[5]	A. limai	Ceará	Partial skull (rostralmost portion).^[7] Possible junior synonym of Irritator challengeri.	A spinosaurid.
Aratasaurus^[8]	A. museunacionali	Ceará	Partial right hindlimb	A coelurosaur.
Irritator^[5]^[9]	I. challengeri	Ceará	Partial skull (posterior half); one of the most complete spinosaurid skulls known	A spinosaurid
Megaraptora indet^[10]	Indeterminate	Unknown	Three sacral vertebrae, two caudal vertebrae, and a partial ilium	A megaraptorid theropod. Originally identified as a possible oviraptorosaur.
Mirischia^[5]	M. asymmetrica	Pernambuco	Pelvis and partial left hindlimb	A compsognathid
Santanaraptor^[5]	S. placidus	Ceará	Some caudal vertebrae, partial pelvis, most of both hindlimbs^[11]	A possible tyrannosauroid

Crocodylomorphs

Crocodylomorphs of the Romualdo Formation
Genus	Species	Presence	Materials	Notes	Images
Araripesuchus	A. gomesii	Romualdo Formation	Type 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.	A uruguaysuchid crocodyloformes	Araripesuchus wegeneri
Caririsuchus	C. camposi	Romualdo Formation		A peirosaurid crocodyliform

Pterosaurs

Pterosaurs of the Romualdo Formation
Genus	Species	Presence	Materials	Notes	Images
Anhanguera	A. araripensis			A pterodactyloid pterosaur	Anhanguera blittersdorffi Anhanguera piscator Cearadactylus atrox Kariridraco dianae Maaradactylus kellneri Tapejara wellnhoferi Thalassodromeus sethi Tropeognathus mesembrinus Tupuxuara leonardii (left) and Tupuxuara longicristatus (right)
	A. blittersdorffi		A complete skull
	A. piscator		A nearly complete skeleton,
	A. robustus
	A. santanae
	A. spielbergi
Araripedactylus	A. dehmi		A single wing bone	A pterodactyloid pterosaur of uncertain affinities
Araripesaurus	A. castilhoi		A partial wing, including distal fragments of the radius and ulna, carpals, all metacarpals and several digits	An ornithocheirid pterosaur
Bakiribu	B. waridza		Two specimens originally thought to have consisted of fragmented upper and lower jaws. May have been parts of the gills of an indeterminate, potentially amiid fish.^[12]	Formerly classified as a ctenochasmatid pterosaur. May have been an indeterminate, potentially amiid ray finned fish.^[12]
Barbosania^[13]	B. gracilirostris		An almost complete skeleton including the skull, that is partially articulated and uncompressed	A targaryendraconian pterosaur
Brasileodactylus	B. araripensis		Several specimen consists of amandible, and the front of a snout and mandible. More complete fossils include a fragmentary skeleton and a skull, with mandible and proximal left wing.	An anhangueria pterosaur
Cearadactylus	C. atrox
Cearadactylus	"C." ligabuei^[14]
Kariridraco	K. dianae		A fairly complete skull, including the lower jaws, and the first four neck vertebrae	A thalassodromid pterosaur
Maaradactylus	M. kellneri		A skull	An anhanguerid pterodactyloid pterosaur
Santanadactylus	S. brasilensis
	?S. pricei
	S. spixi
Tapejara	T. wellnhoferi		Several holotypes consist of a partial skull, a partial mandible (lower jaw), and an anterior (front) cervical (neck) vertebra.	A tapejarid pterosaur
Thalassodromeus	T. sethi		A large skull	A large thalassodromid pterosaur
Tropeognathus	T. mesembrinus		Several holotypes consist of a skull with mandibles, a partial mandible and skeleton with extensive elements of all body parts, except the tail and the lower hindlimbs.	A tropeognathinae pterosaur
Tupuxuara	T. deliradamus		A skull	A thalassodromid pterosaur
	T. leonardii
	T. longicristatus
Unwindia	U. trigonus		A partial skull consisting of only the fused premaxillae and maxillae, some teeth and parts of the palate	A pterodactyloid pterosaur

Turtles

Turtles of the Romualdo Formation
Genus	Species	Presence	Marterials	Notes	Images
Araripemys	A. barretoi		A shell	An araripemydidae turtle^[15]
Brasilemys	B. josai			^[16]
Cearachelys	C. placidoi		A shell	A bothremydinae pleurodiran turtle^[17]
Euraxemys	E. essweini			^[18]
Santanachelys	S. gaffneyi			A protostegidae sea turtle^[19]

Fish

References

↑ Maisey et al., 1991, pp. 99–103
↑ Gibney, Elizabeth (6 March 2014). "Brazil clamps down on illegal fossil trade". Nature. 507 (7490): 20. Bibcode:2014Natur.507...20G. doi:10.1038/507020a. ISSN 0028-0836. PMID 24598620.
1 2 Martill et al., 2007
↑ Martill, 2007
1 2 3 4 5 Weishampel, 2004, pp. 563–570
↑ 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. 84: 107–119. Bibcode:2018CrRes..84..107A. doi:10.1016/j.cretres.2017.10.019. hdl:11336/93821. ISSN 0195-6671.
↑ "Table 4.1," in Weishampel, et al. (2004). Page 73.
↑ Sayão, Juliana Manso; Saraiva, Antônio Álamo Feitosa; Brum, Arthur Souza; Bantim, Renan Alfredo Machado; de Andrade, Rafael Cesar Lima Pedroso; Cheng, Xin; de Lima, Flaviana Jorge; Silva, Helder de Paula; Kellner, Alexander W. A. (2020). "The first theropod dinosaur (Coelurosauria, Theropoda) from the base of the Romualdo Formation (Albian), Araripe Basin, Northeast Brazil". Scientific Reports. 10 (1) 10892. Bibcode:2020NatSR..1010892S. doi:10.1038/s41598-020-67822-9. PMC 7351750. PMID 32651406.
↑ Martill, D. M.; Cruickshank, A. R. I.; Frey, E.; Small, P. G.; Clarke, M. (1 February 1996). "A new crested maniraptoran dinosaur from the Santana Formation (Lower Cretaceous) of Brazil" (PDF). Journal of the Geological Society. 153 (1): 5–8. Bibcode:1996JGSoc.153....5M. doi:10.1144/gsjgs.153.1.0005. ISSN 0016-7649. S2CID 131339386.
↑ Rolando, Alexis M. Aranciaga; Egli, Federico Brissón; 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. 84: 107–119. Bibcode:2018CrRes..84..107A. doi:10.1016/j.cretres.2017.10.019. hdl:11336/93821. S2CID 135256411.
↑ "Table 5.1," in Weishampel, et al. (2004). Page 114.
1 2 Unwin, David M.; Smith, Roy E.; Cooper, Samuel L.A.; Martill, David M. (2026). "Reinterpretation of Bakiribu waridza from the Romualdo Formation (Lower Cretaceous) of Brazil: a fish not a pterosaur". Anais da Academia Brasileira de Ciências. 98 (2). doi:10.1590/0001-3765202620251374. ISSN 1678-2690.
↑ Elgin & Frey, 2011
↑ 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. Bibcode:2002FossR...5..239U. doi:10.5194/fr-5-239-2002.
↑ Araripemys barretoi type locality at Fossilworks.org
1 2 3 4 5 6 7 Chapada do Araripe at Fossilworks.org
↑ Juazeiro do Norte at Fossilworks.org
↑ Crato at Fossilworks.org
↑ Santanachelys gaffneyi at Fossilworks.org
↑ Custódio, M.A.; Guaglio, F.; Warren, L.V.; Simões, M.G.; Fürsich, F.T.; Perinotto, J.A.; Assine, M.L. (2017). "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. 359 (359): 1–15. Bibcode:2017SedG..359....1C. doi:10.1016/j.sedgeo.2017.07.010. hdl:11449/175030.
↑ Casa de Pedra at Fossilworks.org
1 2 3 4 5 6 7 Fara et al., 2005, p.152
↑ Buxéxé, Santana do Cariri at Fossilworks.org
↑ Enneles audax
↑ Iemanja palma
↑ Placidichthys type locality at Fossilworks.org
↑ Maisey, John G. (1 April 2000). "Continental break up and the distribution of fishes of Western Gondwana during the Early Cretaceous". Cretaceous Research. 21 (2): 281–314. Bibcode:2000CrRes..21..281M. doi:10.1006/cres.1999.0195. ISSN 0195-6671.
↑ Ze Gomes at Fossilworks.org

Bibliography

Cavalcanti Duque, Rudah Ruano; Franca Barreto, Alcina Magnólia (2018). "Novos Sítios Fossilíferos da Formação Romualdo, Cretáceo Inferior, Bacia do Araripe, Exu, Pernambuco, Nordeste do Brasil - New Fossiliferous Sites of the Romualdo Formation, Lower Cretaceous, Araripe Basin, Exu, Pernambuco, Northeast of Brazil". Anuário do Instituto de Geociências. 41: 5–14. doi:10.11137/2018_1_05_14. Retrieved 6 October 2018.
Elgin, Ross A.; Frey, Eberhard (20 April 2011). "A new ornithocheirid, Barbosania gracilirostris gen. et sp. nov. (Pterosauria, Pterodactyloidea) from the Santana Formation (Cretaceous) of NE Brazil". Swiss Journal of Palaeontology. 130 (2): 259. Bibcode:2011SwJP..130..259E. doi:10.1007/s13358-011-0017-4. ISSN 1664-2384. S2CID 89178816.
Fabin, Carlos E.; Correia Filho, Osvaldo J.; Alencar, Márcio L.; Barbosa, José A.; de Miranda, Tiago S.; Neumann, Virgínio H.; Gomes, Igor F.; de Santana, Felipe R. (2018). "Stratigraphic Relations of the Ipubi Formation: Siliciclastic-Evaporitic Succession of the Araripe Basin" (PDF). Anais da Academia Brasileira de Ciências. 90 (2 suppl 1): 2049–2071. doi:10.1590/0001-3765201820170526. PMID 29947671. Retrieved 5 October 2018.
Fara, Emmanuel; Saraiva, Antônio Á.F.; Campos, Díogenes de Almeida; Moreira, João K.R.; de Carvalho Siebra, Daniele; Kellner, Alexander W.A. (2005). "Controlled excavations in the Romualdo Member of the Santana Formation (Early Cretaceous, Araripe Basin, northeastern Brazil): stratigraphic, palaeoenvironmental and palaeoecological implications" (PDF). Palaeogeography, Palaeoclimatology, Palaeoecology. 218 (1–2): 145–160. Bibcode:2005PPP...218..145F. doi:10.1016/j.palaeo.2004.12.012. Retrieved 6 October 2018.
Maisey, J.G.; Rutzky, I.; Blum, S.; Elvers, W. (1991). Laboratory Preparation Techniques. In Maisey, j:G. (ed): Santana Fossils: An Illustrated Atlas. Tfh Publications Inc. pp. 99–103. ISBN 0866225498.
Martill, David M.; Bechly, Günter; Loveridge, Robert F. (2007). The Crato Fossil Beds of Brazil: Window into an Ancient World. Cambridge University Press. p. 236. ISBN 978-1-139-46776-6. Retrieved 6 October 2018.
Martill, D.M. (2007). "The age of the Cretaceous Santana Formation fossil Konservat Lagerstätte of north-east Brazil: a historical review and an appraisal of the biochronostratigraphic utility of its palaeobiota". Cretaceous Research. 28 (6): 895–920. Bibcode:2007CrRes..28..895M. doi:10.1016/j.cretres.2007.01.002. Retrieved 6 October 2018.
Weishampel, David B.; Barrett, Paul M.; Coria, Rodolfo A.; Loeuff, Jean Le; Xu, Xing; Zhao, Xijin; Sahni, Ashok; Gomani, Elizabeth M. P.; Noto, Christopher R. (2004). Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds.). Dinosaur distribution (Early Cretaceous, South America): The Dinosauria. Berkeley: University of California Press. pp. 563–570. ISBN 0-520-24209-2.{{cite book}}: CS1 maint: publisher location (link)

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