Romualdo Formation

Romualdo Formation
Stratigraphic range: Early Albian ~
File:Anhanguera santanae.jpg 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
Approximate paleocoordinates
Region	Pernambuco, Piauí & Ceará
Country	Brazil
Extent	Araripe Basin
Romualdo Formation is located in Brazil Romualdo Formation 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.

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

File:Romualdo Formation - outcrop and interpretation.jpg

Outcrop and interpretation of the Romualdo Formation

File:Araripe Basin map - formations and resources.jpg

Extent of the Santana Group, to which the Romualdo Formation belongs, in blue

File:Ipubi and Romualdo Formations - outcrop.jpg

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

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
Aratasaurus	A. museunacionali	Ceará	Partial right hindlimb.	A coelurosaur.	File:Aratasaurus museunacionali.jpg
Irritator	I. challengeri	Ceará	Partial skull (posterior half); one of the most complete spinosaurid skulls known.	A spinosaurid.	File:Irritator Life Reconstruction.jpg
Megaraptora indet.	Indeterminate	Unknown	Three sacral vertebrae, two caudal vertebrae, and a partial ilium.	A megaraptorid theropod. Originally identified as a possible oviraptorosaur.
Mirischia	M. asymmetrica	Pernambuco	Pelvis and partial left hindlimb.	A compsognathid.	File:Mirischia asymmetrica by Ademar Pereira.JPG
Santanaraptor	S. placidus	Ceará	Some caudal vertebrae, partial pelvis, most of both hindlimbs.	A possible tyrannosauroid.	File:Santanaraptor.jpg

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	File:Araripesuchus wegeneri.jpg 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	File:Anhanguera blittersdorffi Life Restoration by Matt Martyniuk.png Anhanguera blittersdorffi File:Anhanguera piscator jconway.jpg Anhanguera piscator File:Cearadactylus.jpg Cearadactylus atrox File:Kariridraco by Júlia d’Oliveira.jpg Kariridraco dianae File:Maaradactylus kellneri.png Maaradactylus kellneri File:Cast of Tapejara wellnhoferi - Pterosaurs Flight in the Age of Dinosaurs.jpg Tapejara wellnhoferi File:Thalassodromeus.jpg Thalassodromeus sethi File:TropeognathusDB22.jpg Tropeognathus mesembrinus File:Tupuxuara.jpg 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 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

Turtles of the Romualdo Formation
Genus	Species	Presence	Marterials	Notes	Images
Araripemys	A. barretoi		A shell	An araripemydidae turtle	File:Araripemys barretoi.JPG
Brasilemys	B. josai
Cearachelys	C. placidoi		A shell	A bothremydinae pleurodiran turtle	File:Cearachelys placidoi MN 01.jpg
Euraxemys	E. essweini
Santanachelys	S. gaffneyi			A protostegidae sea turtle	File:Santanachelys.jpg

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.

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

See also

• List of fossil sites (with link directory)
• List of dinosaur-bearing rock formations
• Araripe Basin
• Cerro Barcino Formation
• Elrhaz Formation
• Guarujá Formation
• Itapecuru Formation
• Mata Amarilla Formation

Further reading

• David M. Martill, 1993. Fossils of the Santana and Crato Formations, Brazil (Field Guide to Fossils no. 5) (The Palaeontological Association)