Romualdo Formation Research Articles

Análise estratigráfica da Formação Brejo Santo, Bacia do Araripe, Nordeste do Brasil: implicações paleogeográficas

The Araripe Basin has been the subject of several publications in the recent years, notably with respect to the rich paleontological collection of Brejo Santo, Crato and Romualdo Formations. However, papers detailing stratigraphic aspects of Brejo Santo Formation are scarce. The formation (Mesozoic era - Dom Joao Stage) is represented by a predominantly pelithic succession (up to 450 m thick) outcropping in eastern portion of the basin. The Brejo Santo Formation unconformably overlies the Cariri Formation, presumably of Paleozoic age, and makes gradational contact with the overlying Missao Velha Formation. It consists of pelithes, such as massive to laminated reddish-brown chalks and calciferous shales with decimetric intercalations of white to greenish-grey siltstones and centimetric layers of reddish mottled, speckled and striped shales, with calcareous nodules, and subordinately, muddy limestones and highly fossiliferous calciferous sandstones and fine sandstones with planar cross-stratifications. The measured paleocurrents have a consistent dispersion pattern for SE, SW and S, suggesting the installation of an open wide basin toward the south. The facies and facies associations described were interpreted as generated by (i) lake systems in which periodically the level of the lakes and/or ponds suffered sudden variations, causing changes in coloration related to seasonal fluctuations in the level of the lake (periods of subaerial exposure) and (ii) ephemeral river systems which fed these lakes. The widespread occurrence of fossil organisms, such as non-marine ostracods and conchostracheans suggest that the sediments of Brejo Santo Formation were possibly deposited in lacustrine-fluviatile systems favorable to the formation of red beds layers, under hot climatic conditions with well-defined dry seasons, corroborating the depositional system interpretation.

A new unusual tapejarid (Pterosauria, Pterodactyloidea) from the Early Cretaceous Romualdo Formation, Araripe Basin, Brazil

ABSTRACTA new unusual tapejarid pterosaur from the Early Cretaceous Romualdo Formation (Araripe Basin, Brazil) is described, based on a skull, lower jaw and some postcranial elements.Caupedactylus ybakagen. et sp. shows the typical high nasoantorbital fenestra of the Thalassodrominae but lacks a palatal ridge, and shares with the Tapejarinae several features, including a downturned rostral end, allowing its allocation to that clade. Furthermore, the new species differs in having an anteriorly and posteriorly expanded premaxillary sagittal crest, the lacrimal process of the jugal strongly inclined, and a slit-like postpalatine fenestra, among other characters. The region of the left jugal-quadratojugal-quadrate shows a pathology that is likely the result of an infection. The lateral surface of the premaxillary crest presents grooves that were interpreted in other pterosaurs as impressions of blood vessels, corroborating growing evidence that cranial crests could have been involved in thermoregulation. Also, the new species has a well-preserved palate with a large palatine forming the anterior region of the choanae and the postpalatine fenestra and a secondary subtemporal fenestra. Since the latter has been regarded as unique to non-pterodactyloids, its occurrence inCaupedactylusdemonstrates that the evolution of palatal region in pterosaurs is more complex than previously thought.

New postcranial elements of the Thalassodrominae (Pterodactyloidea, Tapejaridae) from the Romualdo Formation (Aptian–Albian), Santana Group, Araripe Basin, Brazil

AbstractTapejarids are edentate pterosaurs recovered mainly from Early Cretaceous deposits. They are diagnosed by five synapomorphies, among which only one is postcranial: a broad and well‐developed tubercle at the ventroposterior margin of the coracoid. Regarding the clade Thalassodrominae, most phylogenetic studies are based on cranial elements, as postcranial skeletons of these pterosaurs are rare. Here, new postcranial material from the Romualdo Formation (Aptian–Albian) from the Araripe Basin is described. The material comprises the three posteriormost cervical vertebrae, the first seven dorsal vertebrae (fused into a notarium), both scapulocoracoids, a fragment of a sternum, a partial right humerus, a small fragment of a 4th phalanx of the wing finger, a distal extremity of the right femur and the proximal portions of both tibia and fibula. Comparisons with other specimens and morphological features examined in a phylogenetic context, such as the presence of three foramina lateral and dorsal to the neural canal of the cervical vertebrae, the presence of a notarium and a pneumatic foramen on the ventral side of the proximal portion of the humerus, allow the assignment of this specimen as Thalassodrominae indet. Regarding palaeobiogeographical aspects, to date, this clade is exclusively found in the Romualdo Formation. It is the most complete postcranial material assigned to the Thalassodrominae described so far.

A new fossil caridean shrimp (Crustacea: Decapoda) from the Cretaceous (Albian) of the Romualdo Formation, Araripe Basin, northeastern Brazil.

A new fossil caridean shrimp, Kellnerius jamacaruensis n. gen. n. sp., of the early Cretaceous (Albian) from the Romualdo Formation, Araripe Basin, northeastern Brazil is described and illustrated. The new species is compared to known fossil palaemonids found in Brazil. Kellnerius jamacaruensis n. gen. n. sp. is easily differentiated from the other palaemonids by a rostrum with 5 spines, an enlarged scaphocerite that is longer than the rostrum, and a third somite with a distinct groove in the tergite that does not extend to the pleurite.

The largest flying reptile from Gondwana: a new specimen of Tropeognathus cf. T. mesembrinusWellnhofer, 1987 (Pterodactyloidea, Anhangueridae) and other large pterosaurs from the Romualdo Formation, Lower Cretaceous, Brazil

A very large pterosaur (MN 6594-V) from the Romualdo Formation (Aptian/Albian), Santana Group, Araripe Basin, is described. The specimen is referred to Tropeognathus cf. T. mesembrinus mainly due to the presence of a low and blunt frontoparietal crest, the comparatively low number of teeth and the inclined dorsal part of the occipital region. Two distinct wingspan measurements for pterosaurs are introduced: the maximized wingspan (maxws), which essentially consists of doubling the addition of all wing elements and the length of the scapula or the coracoid (the smaller of the two), and the normal wingspan (nws), which applies a reducing factor (rfc) to the maximized wingspan to account for the natural flexures of the wing. The rfc suggested for pteranodontoids is 5%. In the case of MN 6594-V, the maxws and nws are 8.70 m and 8.26 m, respectively, making it the largest pterosaur recovered from Gondwana so far. The distal end of a larger humerus (MCT 1838-R) and a partial wing (MPSC R 1395) are also described showing that large to giant flying reptiles formed a significant part of the pterosaur fauna from the Romualdo Formation. Lastly, some comments on the nomenclatural stability of the Santana deposits are presented.

A new specimen of the azhdarchoid pterosaur Tapejara wellnhoferi

A new specimen of the Early Cretaceous azhdarchoid Tapejara wellnhoferi is described from the Romualdo Member of the Santana Formation, NE Brazil, providing the first detailed account of the postcranial skeleton. Although limited in its preservation, the osteology is typical of other azhdarchoid pterosaurs from these deposits and represents a juvenile animal with a relatively small wing span of < 1.5 m. The ratios of the pedal elements are identical to those noted for larger, indeterminate azhdarchoids of the Nova Olinda Member of the Crato Formation, where the unguals of the pes are greatly enlarged relative to those of the ornithocheiroids that co-inhabited the Santana lagoon. The ratios of these elements suggest that, as part of a larger suite of characters, these animals were likely better adapted for life on the ground than their ornithocheiroid relatives.

An unusual pterosaur specimen (Pterodactyloidea, ?azhdarchoidea) from the early cretaceous Romualdo formation of Brazil, and the evolution of the pterodactyloid palate.

A new and unusual specimen of a probable azhdarchoid pterosaur is described for the Early Cretaceous (Albian) Romualdo Formation of Brazil. The specimen consists of a palate that, although fragmentary, has a unique morphology differing from all other known pterosaurs with preservation of palatal elements. The new specimen probably indicates the presence of a yet undescribed pterodactyloid taxon for Romualdo Formation and brings new information on pterosaur diversity of this sedimentary unity. Mainly due to the rarity of pterodactyloid specimens with palate preservation, this structure has been overlooked in this clade. Here, we reassess the palatal anatomy of Pterodactyloidea, revealing an intriguing variety of morphotypes and evolutionary trends, some of them described here for the first time. The morphological disparity displayed by different pterodactyloid taxa may be further evidence of the presence of diverse feeding strategies within the clade.

Taxonomy, ontogeny and paleoecology of two species ofHarbiniaTSAO, 1959 (Crustacea, Ostracoda) from the Santana Formation, Lower Cretaceous, northeastern Brazil

The Araripe Basin is the most extensive interior basin in northeastern Brazil, comprising areas of Ceará, Piauí and Pernambuco states. The Santana Formation, attributed to the Aptian–?lower Albian age of the basin, is subdivided into two members, Crato and Romualdo, which bear an abundant fossil record of plant fragments, arthropods and vertebrates, especially 3D-preserved fishes. The present study focuses on the taxonomy, ontogeny and paleoecology of two ostracode species from the Romualdo Member and the top section of the Crato Member (Ipubi layers),Harbinia salitrensis(Krömmelbein and Weber, 1971) emend. andH. altanew species. The ontogenetic series for both species are illustrated, except for the A-8 instar;H. salitrensisis also redescribed. The present work is also the first to produce quantitative information about the paleoecology of the Santana Formation based on ostracode populations. The results obtained from analyses of the population age-structure of both species, in addition to dominance (Simpson) and diversity index (Shannon) values, corroborated previous data on the studied sequence. According to these results, the strata were deposited in a limnic, low-to-moderate energy environment with salinity levels varying from oligohaline to mesohaline. The new data indicate the possibility of these environments also being hypersaline.

A Nearly Complete Ornithocheirid Pterosaur from the Aptian (Early Cretaceous) Crato Formation of NE Brazil

A partial ornithocheirid, representing a rare example of a pterosaurian body fossil from the Nova Olinda Member of the Crato Formation, NE Brazil, is described from the collections of the State Museum of Natural History, Karlsruhe. While similar in preservation and taphonomy to Arthurdactylus conandoylei, it is distinguished by slight differences in biometric ratios, but the absence of a skull prevents closer identification. Mostly complete body fossils belonging to ornithocheiroid pterosaurs appear to be relatively more abundant in the younger Romualdo Member of the Santana Formation, making the described specimen one of only two well documented ornithocheiroids known from the Nova Olinda Lagerstatte.

Novos equinoides (Echinodermata: Echinoidea) do Albiano da Bacia do Araripe, nordeste do Brasil

In this paper are registered the Echinoidea species Douvillaster benguellensis (Loriol 1888) and Hemiaster proclivus Cotteau, Peron & Gauthier 1878 in the upper beds of the Romualdo Member, Santana Formation (Albian), from the Rancharia District, Pernambuco State, western portion of the Araripe Basin. With this registry, extends the geographical paleodistribution of these species, before found in the Riachuelo Formation (Aptian-Albian) and in the Sergipe-Alagoas Basin in Brazil, and Catumbela Formation from the Benguela Basin in Angola. According to the functional morphology of the shells, in the Araripe Basin, H. proclivus had lived inner of sand substrate in shallow marine environment, and D. benguellensis had lived almost as an endofaunal organism in deeper environment, where the circulation and oxygenation of the water conditions were more restricted.

A wildfire origin for terrestrial organic debris in the Cretaceous Santana Formation Fossil Lagerstätte (Araripe Basin) of north-east Brazil

The late Early Cretaceous Santana Formation fossil Lagerstätte of north-east Brazil’s Araripe Basin is known for its diverse aquatic vertebrate assemblage, but little is known of the palaeoenvironment of the surrounding hinterland of the basin. Isolated gymnosperm tracheids in acid-resistant residues from concretions of Romualdo Member of the Santana Formation are composed of fusain consistent with a wildfire origin. Fusain debris probably entered the Araripe Basin as fallout from wind-blown ash. A wildfire origin for the organic debris is consistent with palaeoclimatic interpretations that indicate an arid hinterland for the Araripe Basin during the mid Cretaceous.

On the osteology of Tapejara wellnhoferi KELLNER 1989 and the first occurrence of a multiple specimen assemblage from the Santana Formation, Araripe Basin, NE-Brazil

The postcranial elements of two similar sized and juvenile individuals, along with a partial skull, are attributed to the Early Cretaceous pterosaur Tapejara wellnhoferi. The remains, recovered from a single concretion of the Romualdo Member, Santana Formation, NE-Brazil, represent the first account of multiple specimens having settled together and allow for a complete review of postcranial osteology in tapejarid pterosaurs. A comparison of long bone morphometrics indicates that all specimens attributed to the Tapejaridae for which these elements are known (i.e. Huaxiapterus, Sinopterus, Tapejara) display similar bivariate ratios, suggesting that Chinese and Brazilian taxa must have exhibited similar growth patterns. An unusual pneumatic configuration, whereby the humerus is pierced by both dorsally and ventrally located foramina, is observed within T. wellnhoferi, while the pneumatic system is inferred to have invaded the hindlimbs via the femur in all members of the Azhdarchoidea. The partial preservation of the endocranial cavity allows for a reconstruction of the tapejarid brain, where despite a small orbit with respect to skull size, the presence of large flocculi and ocular lobes indicate that Tapejara possessed both excellent balancing and visual systems as a consequence of its aerial lifestyle.

First turtle from the Ipubi Formation (Early Cretaceous), Santana Group, Araripe Basin, Brazil

The Araripe Basin is located in northeastern Brazil between the states of Ceara, Piaui and Pernambuco (Figure 1). The Crato and Romualdo formations (Santana Group, see details in Neumann & Cabrera, 1999; Valenca et al., 2003) that comprise the most fossiliferous strata of this basin, are famous worldwide for the diverse and exquisitely well preserved fossil assemblages (e.g. Maisey, 1991). These two different lagerstatten were formed during the Lower Cretaceous, Aptian/Albian (Pons et al., 1990; ABSTRACT – Up to date turtle remains from the Early Cretaceous Santana Group are known only to the Crato and Romualdo formations (Aptian-Albian) that have yielded five species: Araripemys barretoi Price, 1973; Santanachelys gaffneyi Hirayama, 1998; Brasilemys josai Lapparent de Broin, 2000; Cearachelys placidoi Gaffney, Campos & Hirayama, 2001 and Euraxemys essweini Gaffney, Tong & Meylan, 2006. Except for A. barretoi, known from both, the Romualdo and Crato formations, all other turtle taxa are restricted to the Romualdo Formation. Fragments of the skull, an incomplete lower jaw and carapace of the first turtle remains from the Ipubi Formation are reported here. This material was collected in the shales above the gypsum layer, close to the contact with the Romualdo Formation (Aptian-Albian). Compared to other turtles from the Santana Group, this specimen is referred to Pelomedusoides, excluding Araripemys and Brasilemys, based on the following characteristics: absence of a cavum pterygoidei, absence of cervical scute, absence of fontanels in the carapace, contact between nuchal and first peripheral, and absence of nuchal emargination.

CONTROLLED EXCAVATIONS IN THE ROMUALDO FORMATION LAGERSTATTE (ARARIPE BASIN, BRAZIL) AND PTEROSAUR DIVERSITY: REMARKS BASED ON NEW FINDINGS

Because of its fossil abundance and exceptional preservation, the Romualdo Formation of the Santana Group has become a famous lithostratigraphic unit of the Araripe Basin. In the past decades, much research has been conducted on the vertebrates of this unit, especially fish and pterosaurs, based mainly on museum collections. Despite the importance of these fossil finds, no stratigraphic information is known about them, because until recently, locals have collected most of the fossils. Here we present the results of the third controlled excavation of these layers. The data from all fossils collected confirm a faunal succession of fish biota. In the upper and most fossiliferous layer, the faunal composition shows a pattern of fish distribution never observed before, indicating that previous categories (abundance versus diversity) do not include the total diversity of fish populations. Pterosaur remains were recorded for the first time in the field, contradicting the general idea that these volant reptiles are common in the Romualdo strata. The specimen was attributed to the clade Anhangueridae because the proportional length of the first wing phalanx is less than twice the length of the wing metacarpal. The controlled excavation showed that the pterosaur assemblages from this formation probably occur in clusters. The known abundance of pterosaurs in the Romualdo Formation has been biased by just a few sites of fossil extraction, and these reptiles do not appear to have been as widespread or abundant as previously thought.

Taxonomic remarks on Brazilian Cretaceous Decapoda from Araripe Basin, Brazil, and ecological inferences

Beurlenia araripensis Martins-Neto and Mezzalira, 1991 (Decapoda: Caridea) and Paleomattea deliciosa Maisey and Carvalho, 1995 (Decapoda: Penaeoidea) are reviser baseated upon new and better preserved samples. The new specimens were found in the Santana Formation, Araripe Basin, Northeast Brazil, respectively in the Crato and Romualdo members. B. araripensis is represented by a well preserved specimen, where is possible to see a cephalothorax with antennal and branchiostegal spines, rostrum with 14 dorsal spines, and telson with posterior spines. This material permits a better characterization of the species’ morphology and its placement in Palaemonidae. The Dendrobranchiata material of P. deliciosa, found in the bituminous shale of Romualdo Member, is for the fi rst time recorded in clusters of fragmentary parts that suggest mass mortality and morphologies that point to a planktonic lifestyle, as occurs with extant forms of sergestids.

Santanasalmo elegans gen. et sp. nov., a basal euteleostean fish from the Lower Cretaceous of the Araripe Basin, northeastern Brazil

The bituminous shales from the Pedra Branca mine have yielded certain taxa also found in the carbonate concretions of the Romualdo Member (Santana Formation) and in the plattenkalk of the Crato Formation in northeastern Brazil. Based on two specimens obtained from this locality, we describe a small and slender fish, Santanasalmo elegans gen. et sp. nov. It can be recognized by a combination of features: elongate head with prominent snout, reduced orbit, very long and arched antorbital, edentulous jaws, boomerang-shaped preopercle with right vertical arm, caudal endoskeleton with at least five hypurals, high position of the lateral line on the flank. According to a set of characters, the fish remains as a basal Euteleostei incertae sedis.

A new crocodylomorph specimen from the Araripe Basin (Crato Member, Santana Formation), northeastern Brazil

The fossil fauna of the Santana Formation (Early Cretaceous) comprises many distinct taxa, but crocodylomorphs are poorly understood. Here we describe a new specimen (MPSC-R1137) that consists of a complete hind limb found in the Crato Member, the basal section of the Santana Formation. Based on the characteristics of the fibula (e.g., pronounced variation of the shaft width) and length proportions of the femur and tibia, this specimen can be distinguished from Caririsuchus camposi and Araripesuchus gomesii, which are known from the Romualdo Member (the upper lithostratigraphic unit of the Santana Formation). The only crocodylomorph formally described from the Crato Member is Susisuchus anatoceps, whose holotype lacks elements of the hind limb. On the basis of a comparative anatomical study of the hind limb, which shows no similarities between MPSC-R1137 and other crocodylomorphs from the Araripe Basin, we tentatively classify this new specimen as cf. Susisuchus sp., and provide new anatomical information for this rather derived crocodylomorph.

Mass mortality of fishes in the Santana Formation (Lower Cretaceous, ?Albian) of northeast Brazil

Abundant and well-preserved fish occur at intervals within the Romualdo Member of the Santana Formation (?Albian, Early Cretaceous) in the Araripe Basin, northeast Brazil. Preservation of large numbers of articulated individuals of similar size on a single bedding plane is consistent with the mass mortality of fish shoals over short time intervals (days or weeks). Preservation can be exceptional, with some individuals having traces of soft tissues preserved, including musculature, gut lining, gut contents and pigment of the eyes. Mass mortality assemblage density can be high, such that fossils may produce a single layer within millimeter-laminated concretions, constituting a fish bone-bed. The causes of the mass mortalities are difficult to determine but may have been multi-factorial, including changes in surface water oxygenation or salinity. Toxification of the water column by release of H 2S from sediments or by toxic dinoflagellate or cyanobacterial blooms may also have been involved but firm evidence is lacking.

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

This paper is concerned with the famous fossil-bearing carbonate concretions of the Romualdo Member of the Santana Formation Konservat Lagerstätten of north-east Brazil. This palaeontologically important horizon was first dated as Cretaceous by the French palaeoichthyologist Louis Agassiz on the basis of fish fossils obtained by Bavarian explorers Spix and Martius between 1817 and 1820 and Scottish botanist and explorer George Gardner between 1836 and 1841. Gardner equated the concretion level with the English Albian ‘Upper Greensands’ on the basis of an imagined similarity of stratigraphic sequence with that of the Isle of Wight, southern England. Since then high precision dating of this remarkable deposit has proved elusive and the concretion-bearing part of the Santana Formation has been variously dated as early Late Cretaceous or late Early Cretaceous. Attempts at greater precision over the last 30 years have cited its age variously as Aptian, Albian or possibly Cenomanian, but few reliable data have been presented to support these dates.

A new side-necked turtle (Pleurodira, Pelomedusoides) from the Santana Formation (Early Cretaceous), Araripe Basin, Northeastern Brazil

The fossil fauna of turtles from the Santana Formation, Araripe Basin, Early Cretaceous from Northeastern Brazil, includes, to exception of the Santanachelys gaffneyi (Cryptodira, Protostegidae), only pelurodiran taxa. A new genus and species, Caririemys violetae gen. et sp. nov. (Pleurodira, Pelomedusoides), from the Romualdo Member, upper section of the Santana Formation, is described here. Caririemys is based on one specimen consisting of a carapace, several vertebrae, a right femur and a right pelvis. Caririemys differs of the other pleurodirans from the Santana Formation by the following combination of characters: oval and moderately domed carapace; complete neural series reaching the suprapygal; and neural plate 8 shows an extensive contact with costal 7 and 8. This new taxon enhances the turtle diversity of the Santana Formation, which is presently the most diverse deposit of Mesozoic Testudines in the country.