Walking in the Gondwanic Floodplains of Rio do Peixe Basins

The Rio do Peixe basinsRio do Peixe basins are the set of four associated basins: Sousa, Uiraúna-Brejo das FreirasUiraúna-Brejo das Freiras basin (also known as Triunfo), Pombal and Vertentes. They are located in the western Paraíba StateParaíba state and in the Ceará State, northeastern BrazilBrazil, in a total area of ~1,280 km2. The origin of these basins (Lower Cretaceous, BerriasianBerriasian to lower BarremianBarremian) is related to normalNormal fault and transcurrent faultTranscurrent fault movements along preexisting structural trends of the Proterozoic basementProterozoic basement during the South and EquatorialEquatorial Atlantic OceanAtlantic ocean opening. Dinosaur footprints are the most abundant fossils in the siliciclastic continental sediments. The main tetrapod ichnofaunaIchnofauna comprises, in at least 42 individual tracksites through approximately 96 stratigraphic levels, isolate footprints and trackways of large and small theropodsTheropods, besides ornithopodsOrnithopods, sauropodsSauropods, and rare ankylosaursAnkylosaur. There are also invertebrate ichnofossils. The body fossils are fish scales and bone fragments, but also rare dinosaur and CrocodylomorphaCrocodylomorpha bones, palynomorphsPalynomorphs, plantPlants fragments, ostracodsOstracods and conchostracansConchostracans. These basins comprise a lot of dinosaur ichnofaunasIchnofauna, in the same stratigraphic-time-paleogeographical context, and they represent segments of a widespread megatracksiteMegatracksite. There are 447 theropodTheropods tracks; 90 sauropodsSauropods (Total of 537 saurischiansSaurischians); 2 quadrupedal ornithischiansOrnithischians (one of them an ankylosaurian); 6 small ornithopodsOrnithopods; 30 graviportal ornithopodsOrnithopods (total of 38 ornithischiansOrnithischians); one track of a juvenile biped dinosaur; about 53 unclassifiable dinosaur tracks (629 dinosaurs, all together); a hand-foot set of batrachopodidBatrachopodids prints; traces of a CrocodylomorphaCrocodylomorpha; an isolate lacertoid printLacertoid print; and a large number of small chelonianChelonians half-swimming tracksHalf-swimming tracks. The environmental setting indicates an endemic biotaEndemic biota living nearby ephemeral riversRivers and shallow lakesLake under hot climateHot climate conditions. These were preserved in alluvial fansAlluvial fan, braided, meandering riversMeandering rivers and shallow lakeLake deposits of BerriasianBerriasian to lower BarremianBarremian ages. Dinosaur faunas (both as bone remains and as ichnofaunasIchnofauna) from the Early Cretaceous are quite rare in the world, and the material discovered in these basins is important to the knowledge of the dinosaur diversityDinosaur diversity during the Cretaceous.