Deep-scaled fish (Osteichthyes: Actinopterygii) from the lower Permian (Cisuralian) lacustrine deposits of the Parnaíba Basin, NE Brazil

New Chondrichthyes fin spines fossils from the Pedra de Fogo Formation (Permian) in State of Tocantins, Brazil. The Parnaíba Basin has a unique fossil record of Chondrichthyes that lived during the Permian period. Within this basin is the Pedra de Fogo Formation, dating from the Cisuralian, which is distributed in parts of the states of Pará, Tocantins, Piauí, Maranhão, Ceará, and Bahia. Due to their cartilaginous skeleton, Chondrichthyes skeletal remains are not prone to fossilization, with teeth, fin spines and dermal denticles being more commonly found. The main objective of this work is to describe new fins spines from the Parnaíba Basin, collected in the State of Tocantins and stored at the Museum of Archeology and Paleontology of the Federal University of Piauí. Six shark spines were identified as belonging to Ctenacanthiformes. A more specific classification at the genus and species level is still uncertain due to the difficulties with the definition of such taxa and incompleteness of the described remains. These occurrences contribute to future research in the area concerning about on fossil fin spines found in the Parnaíba Basin. Keywords: Ctenacanthus, Ctenacanthiformes, paleohistology, Paleozoic.

Palygorskite is a clay mineral with structural units forming ribbons, whose economic importance is directly related to its unusual structure and physicochemical properties, which give it a wide variety of uses in industry. The formation stability field of palygorskite is very limited, which makes deposits of this clay rare around the world. In Brazil, the only exploitable deposits of this mineral are located in the municipality of Guadalupe, Piauí state, inserted in the geological context of the Parnaíba Basin, specifically in the Carboniferous and Permian sequence represented by the Piauí, Poti and Pedra de Fogo formations. The objective of this study was the geological and mineralogical description of palygorskite occurrences in the Guadalupe region. Six occurrences were studied, and 25 samples were collected. These raw samples were processed to concentrate particles with size smaller than 44 µm. XRD, SEM/EDS, density and particle size analysis were performed. Most of the samples were composed of palygorskite, quartz and kaolinite; however, according to the diffractograms, there are three samples with the absence of palygorskite, two with the absence of kaolinite and one with presence of dolomite. From these results, it is possible to correlate hypotheses for palygorskite formation with the local geological context. The environmental conditions of Piauí and Pedra de Fogo formations were favorable to this clay mineral formation, the association of dolomite and palygorskite in an upper layer may indicate a greater association with Pedra de Fogo Formation, however the field descriptions, as the levels of silexite, and the analyses results are not enough to define in which one of these formations the occurrences of palygorskite are inserted.

New petrified gymnosperms from the Permian of Maranhão (Pedra de Fogo Formation), Brazil: Ductolobatopitys nov. gen. and Kaokoxylon

The Serra da Cangalha impact structure, Brazil: Geological, stratigraphic and petrographic aspects of a recently confirmed impact structure

Shallow lacustrine system of the Permian Pedra de Fogo Formation, Western Gondwana, Parnaíba Basin, Brazil

New petrified forest in Maranhão, Permian (Cisuralian) of the Parnaíba Basin, Brazil

The Pedra de Fogo Formation, of Permian age, which is situated within the Parnaiba Basin, is well know for its content of fossil trunks, principally of the Genus Psaronius. However, in recent years, other genera have been found with some frequency. The occurrence of 33 permineralised fossil trunks, preserved in growth position on the right hand margin of the poti River, in the city of Teresina, Piaui, is reported here. This paper details the area of occurrence of the fossil trunks and describes briefly the characteristics of the sedimentary facies, which suggest a transitional (marine-continental) depositional environment. One wood specimen, belonging to a new genus and a new species (Teresinoxylon euzebioi Mussa) is described; it shows close affinity with the Cycadoxyleae. A probable Lower Middle Permian age can be assigned to the specimens from this important and rare fossiliferous site and it is requested here that the authorities act promptly to ensure its preservation.

The “Pedra de Fogo” Formation dated from the Permian period (approximately 280 million years ago), belongs to the sedimentary Parnaiba Basin, located in the northeastern region of Brazil. It is recognized by their well preserved fossil contents and it is notable for having several fossilized trunks in the growing position. Specimens from different localities were selected in order to perform spectroscopic studies and X-ray diffraction analysis, as well, for the purpose of identifying and characterizing compounds related to the fossilized materials. These different techniques allowed to obtain information from the molecular spectra in organic and inorganic substances, which are present in these above stated fossils and in the atomic elements, as well as the crystalline phases. These aforementioned studies have revealed promising paleoenvironmental interpretations about their depositional strata. Regarding the techniques, these have enabled inferences with respect to the fossil diagenetic events and allowed a better understanding of the fossilized process and the mineralogical characteristics of the living environment, where the plants were buried. This study presents physical and/or chemical properties of the fossilized plants through vibrational spectroscopies, SEM/EDS spectroscopy and X-ray diffraction techniques. Based on the results duly obtained, we were able to identify the presence of silica and confirm that the dominant process of the fossilized specimens investigated has occurred through quartz silicification with the contribution of persistence from amorphous carbon.

Two new petrified gymnosperms with solenoid piths from the Pedra de Fogo Formation, Permian of Maranhão, Brazil

A taphofacies model for coquina sedimentation in lakes (Lower Cretaceous, Morro do Chaves Formation, NE Brazil)

Fossil fish remains from the Pedra de Fogo Formation in Brazil are abundant and diversified, yet studies of fossils from this lithostratigraphic unit in the Tocantins State remain scarce. Here we describe the general morphology and histology of actinopterygian remains collected in Filadelfia municipality, Tocantins State. These new records comprise isolated teeth and scales found at about the same biostratigraphic level. Our morphologic analysis of scales reveals five distinct body regions. Comparative and histological analysis of the ganoid scales point to the palaeoniscoid type, confirming a palaeonisciform contribution. Additionally, teeth histology confirms the presence of simplexodont plicidentine, indicating a possible morphofunctional adaptation to predatory life. The discovery of more complete specimens is necessary to refine taxonomic assignment.

This is the first record of callipterids, sensu stricto, in South America, Western Gondwana. Previously, they were known only from the palaeoequatorial belt, including the Euroamerican (North America and Europe), northernmost African, and Cathaysian (northern China, Southeast Asia, and the Malay Archipelago) regions, or from north of Pangaea (Siberia), during the latest Carboniferous–late Permian interval. In the present study, fossils were collected from sediments from the middle–upper Pedra de Fogo Formation, part of the Permian of the Parnaíba Basin in eastern Maranhão State, northeastern Brazil. The material recovered can be attributed to the callipterid genus Rhachiphyllum, and specifically to the species Rhachiphyllum schenkii (Heyer) Kerp. In addition, we found an Autunia-like fructification, corroborating a peltasperm affinity. The presence of R. schenkii could be indicative of an early Permian age for the Pedra de Fogo Formation since this species has a short and well-determined stratigraphic range in Europe. Palaeogeographically, the above-mentioned species found in association with fern genus Pecopteris suggests a migration corridor running from central Europe and northern South America during Permian times.KeywordsCallipteridsPermianWestern GondwanaPedra de Fogo FormationNortheastern Brazil

New chondrichthyan fin spines from the Pedra de Fogo Formation, Brazil

It has long been recognized that presence–absence, localisation, size, number and shape of fish scales can be important taxonomic features. Although there are some notes on the relationship between scale morphology and ecological needs, in the absence of a sufficiently large and detailed database, the morphological variability of fish scales and the factors responsible for this variability have not yet been explored in detail. For this reason, a database—which contains the shape and relative size data of 193 freshwater fish taxa of 14 orders, originated from five biogeographic realms—has been built. Database analyses showed that both the scale shape and relative size are proper taxonomic indicators. They can be used to separate higher taxonomic categories (e.g., orders), and by the simultaneous analysis of shape and size scale morphology, we showed increased sensitivity for species‐level detachments. Our results suggest that while both the shape and the size of the fish scales are genetically determined, they are also useful descriptors of the niche segregation (habitat use, flow preference) of close relative species. Scale morphology is a promising additional tool to specify the environmental preferences of lesser known or close relative recent and extinct fish species. And also can be of great help in such cases when only the scales are available for taxonomic identification, for example, in the research field of archaeology and palaeontology.

ABSTRACTBrazilichthys macrognathus is the only named actinopterygian from the Permian (Cisuralian) Pedra de Fogo Formation of northeastern Brazil, in which it is represented by a single three-dimensionally preserved, but incompletely described, skull of unclear systematic placement. We used X-ray micro-computed tomography (µCT) to redescribe its anatomy, in particular parts of the internal skeleton, and assess its phylogenetic affinities. We correct errors in the original description, including the number of infraorbital bones and the misidentification of the dermosphenotic as sclerotic ossifications. These reinterpretations of external anatomy are accompanied by new data on internal structure, including the palate, the parasphenoid, and the branchial and hyoid arches. A maximum parsimony analysis of anatomical data resolves Brazilichthys as a stem actinopterygian, crownward of all Devonian species. This placement is supported by the absence of a dermosphenotic posterior ramus and the presence of opercular process of the hyomandibula. A similar placement is suggested by a Bayesian analysis of the same data set, although relationships throughout the tree are less resolved. Our results reject previous interpretations of Brazilichthys as a relative of Birgeriidae, a Triassic group traditionally placed within the actinopterygian crown. Although Acrolepis is too poorly known to be included in our analysis, we also reject relationship between that taxon and Brazilichthys, because their only shared similarities appear to be broadly distributed among early actinopterygians.