Romualdo Formation
Brazilian geologic formation
title: "Romualdo Formation" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["romualdo-formation", "geologic-formations-of-brazil", "cretaceous-brazil", "cretaceous-paleontological-sites-of-south-america", "paleontology-in-brazil", "mudstone-formations-of-brazil", "deltaic-deposits", "environment-of-ceará", "environment-of-pernambuco", "environment-of-piauí", "landforms-of-ceará", "landforms-of-pernambuco", "landforms-of-piauí", "northeast-region,-brazil"] description: "Brazilian geologic formation" topic_path: "philosophy" source: "https://en.wikipedia.org/wiki/Romualdo_Formation" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0
::summary Brazilian geologic formation ::
::data[format=table title="Infobox rockunit"]
| Field | Value |
|---|---|
| name | Romualdo Formation |
| image | Anhanguera santanae.jpg |
| caption | Fossils of Anhanguera (top) and Santanadactylus (bottom) from the Romualdo Formation |
| type | Geological formation |
| age | Early Albian |
| ~ | |
| period | Aptian |
| prilithology | Mudstone |
| otherlithology | Limestone, shale |
| region | Pernambuco, Piauí & Ceará |
| country | Brazil |
| coordinates | |
| paleocoordinates | |
| unitof | Santana Group |
| underlies | Exu & Arajara Formations |
| overlies | Crato & Ipubi Formations |
| thickness | 2 - |
| extent | Araripe Basin |
| map | {{Location map+ |
| relief | 1 |
| width | 250 |
| float | center |
| lat_deg | -7.2 |
| lon_deg | -39.3 |
| mark | Green pog.svg |
| marksize | 12 |
| :: |
| name = Romualdo Formation | image = Anhanguera santanae.jpg | caption = Fossils of Anhanguera (top) and Santanadactylus (bottom) from the Romualdo Formation | type = Geological formation | age = Early Albian ~ | period = Aptian | prilithology = Mudstone | otherlithology = Limestone, shale | namedfor = | namedby = | region = Pernambuco, Piauí & Ceará | country = Brazil | coordinates = | paleocoordinates = | unitof = Santana Group | subunits = | underlies = Exu & Arajara Formations | overlies = Crato & Ipubi Formations | thickness = 2 - | extent = Araripe Basin | area = | map = {{Location map+ | Brazil | relief = 1 | width = 250 | float = center | places = | lat_deg = -7.2 | lon_deg = -39.3 | mark = Green pog.svg | marksize = 12 | map_caption =
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.
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.
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
::figure[src="https://upload.wikimedia.org/wikipedia/commons/a/a9/Romualdo_Formation_-_outcrop_and_interpretation.jpg" caption="Outcrop and interpretation of the Romualdo Formation"] ::
::figure[src="https://upload.wikimedia.org/wikipedia/commons/e/e5/Araripe_Basin_map_-_formations_and_resources.jpg" caption="Extent of the Santana Group, to which the Romualdo Formation belongs, in blue"] ::
::figure[src="https://upload.wikimedia.org/wikipedia/commons/3/3c/Ipubi_and_Romualdo_Formations_-_outcrop.jpg" caption="Outcrop of the Romualdo and Ipubi Formations"] ::
Main article: Santana Group#Basin history
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.
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.
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.
Dinosaurs
::data[format=table]
| Dinosaurs of the Romualdo Formation | Genus | Species | Presence | Materials | Notes | Images |
|---|---|---|---|---|---|---|
| Angaturama | A. limai | Ceará | Partial skull (rostralmost portion). Possible junior synonym of Irritator challengeri. | A spinosaurid. | [[File:Angaturama limai skeleton.jpg | center |
| Aratasaurus | A. museunacionali | Ceará | Partial right hindlimb. | A coelurosaur. | [[File:Aratasaurus museunacionali.jpg | center |
| last1=Martill | first1=D. M. | last2=Cruickshank | first2=A. R. I. | last3=Frey | first3=E. | last4=Small |
| last1=Rolando | first1=Alexis M. Aranciaga | last2=Egli | first2=Federico Brissón | last3=Sales | first3=Marcos A.F. | last4=Martinelli |
| Mirischia | M. asymmetrica | Pernambuco | Pelvis and partial left hindlimb. | A compsognathid. | [[File:Mirischia asymmetrica by Ademar Pereira.JPG | center |
| Santanaraptor | S. placidus | Ceará | Some caudal vertebrae, partial pelvis, most of both hindlimbs. | A possible tyrannosauroid. | [[File:Santanaraptor.jpg | center |
| :: |
Crocodylomorphs
::data[format=table]
| 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 | [[File:Araripesuchus wegeneri.jpg | center |
| Caririsuchus | C. camposi | Romualdo Formation | A peirosaurid crocodyliform. | |||
| :: |
Pterosaurs
::data[format=table]
| Pterosaurs of the Romualdo Formation | Genus | Species | Presence | Materials | Notes | Images |
|---|---|---|---|---|---|---|
| Anhanguera | A. araripensis | A pterodactyloid pterosaur | [[File:Anhanguera blittersdorffi Life Restoration by Matt Martyniuk.png | thumb | ||
| 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 specimen consists of fragmented upper and lower jaws | A ctenochasmatid pterosaur | |||
| Barbosania | 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 | |||||
| "C." ligabuei | ||||||
| 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 consists 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 conists of a skull with manidles, 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 only the fused premaxillae and maxillae, some teeth and parts of the palate | A pterodactyloid pterosaur | |||
| :: |
Turtles
::data[format=table]
| Turtles of the Romualdo Formation | Genus | Species | Presence | Marterials | Notes | Images |
|---|---|---|---|---|---|---|
| Araripemys | A. barretoi | A shell | An araripemydidae turtle | [[File:Araripemys_barretoi.JPG | center | |
| Brasilemys | B. josai | |||||
| Cearachelys | C. placidoi | A shell | A bothremydinae pleurodiran turtle | [[File:Cearachelys placidoi MN 01.jpg | center | |
| Euraxemys | E. essweini | |||||
| Santanachelys | S. gaffneyi | A protostegidae sea turtle | [[File:Santanachelys.jpg | center | ||
| :: |
Fish
- Araripelepidotes
- Axelrodichthys araripensis.
- Beurlenichthys ouricuriensis
- Brannerion
- Calamopleurus
- Cladocyclus
- Enneles audax
- Iemanja palma
- Lepidotes wenzai
- Microdon penalvai
- Notelops
- Obaichthys
- Oshunia brevis
- Placidichthys bidorsalis
- Rhacolepis
- Iansan beurleni
- Santanaclupea silvasantosi
- Tharrhias
- Tribodus limae
- Vinctifer
References
Bibliography
References
- Maisey et al., 1991, pp. 99–103
- Gibney, Elizabeth. (2014-03-06). "Brazil clamps down on illegal fossil trade". Nature.
- Martill et al., 2007
- Martill, 2007
- (2018). "A supposed Gondwanan oviraptorosaur from the Albian of Brazil represents the oldest South American megaraptoran". Cretaceous Research.
- Weishampel, 2004, pp. 563–570
- "Table 4.1," in Weishampel, et al. (2004). Page 73.
- (2020). "The first theropod dinosaur (Coelurosauria, Theropoda) from the base of the Romualdo Formation (Albian), Araripe Basin, Northeast Brazil". Scientific Reports.
- (1996-02-01). "A new crested maniraptoran dinosaur from the Santana Formation (Lower Cretaceous) of Brazil". Journal of the Geological Society.
- (2018). "A supposed Gondwanan oviraptorosaur from the Albian of Brazil represents the oldest South American megaraptoran". Cretaceous Research.
- "Table 5.1," in Weishampel, et al. (2004). Page 114.
- 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.
- [https://paleobiodb.org/classic/displayCollResults?collection_no=128565 ''Araripemys barretoi'' type locality] at [[Fossilworks]].org
- [https://paleobiodb.org/classic/displayCollResults?collection_no=92290 Chapada do Araripe] at [[Fossilworks]].org
- [https://paleobiodb.org/classic/displayCollResults?collection_no=128568 Juazeiro do Norte] at [[Fossilworks]].org
- [https://paleobiodb.org/classic/displayCollResults?collection_no=83306 Crato] at [[Fossilworks]].org
- [https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=90355 ''Santanachelys gaffneyi''] at [[Fossilworks]].org
- Custódio, M.A.. (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.
- [https://paleobiodb.org/classic/displayCollResults?collection_no=133574 Casa de Pedra] at [[Fossilworks]].org
- Fara et al., 2005, p.152
- [https://paleobiodb.org/classic/displayCollResults?collection_no=28052 Buxéxé, Santana do Cariri] at [[Fossilworks]].org
- [http://palaeo.gly.bris.ac.uk/Palaeofiles/Lagerstatten/santana/FosCrd25.htm ''Enneles audax'']
- [http://palaeo.gly.bris.ac.uk/Palaeofiles/Lagerstatten/santana/FosCrd6.htm ''Iemanja palma'']
- [https://paleobiodb.org/classic/displayCollResults?collection_no=124310 ''Placidichthys'' type locality] at [[Fossilworks]].org
- Maisey, John G.. (2000-04-01). "Continental break up and the distribution of fishes of Western Gondwana during the Early Cretaceous". Cretaceous Research.
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