Dinosaur tracks from the Sitio Pereiros ichnosite, Triunfo Basin (Lower Cretaceous) and the dinosaur diversity in the Rio do Peixe basins, Northeastern Brazil

The dinosaur tracks in the Rio do Peixe basins (Lower Cretaceous, Rio da Serra-Aratu stages) occur in at least 39 individual tracksites through approximately 98 stratigraphic levels in the western part of the State of Paraiba, Brazil. The Triunfo basin (one of the four Rio do Peixe basins) is a 480 km(2) asymmetric graben, located in the counties of Sao Joao do Rio do Peixe, Uirauna, Poco, Brejo das Freiras, Triunfo, and Santa Helena, controlled by a NE transcurrent fault system. To date, only four isolated footprints and two incomplete trackways have been identified in the Antenor Navarro Formation. Among the isolated footprints, three probably belong to theropods. One incomplete trackway consists of just two digitigrade, rounded digits, suggesting they were made by a small ornithopod. In this study we describe a new ichnosite, located at Sitio Pereiros, Sao Joao do Rio do Peixe county, Paraiba State. The one and a half meter thick succession of fine-grained sandstones, siltstones, mudstones and shales with ripple marks, climbing ripples and mud cracks of the Sousa Formation reveals a bedding plane with three trackways, with a total of 19 tridactyl, mesaxonic footprints. These trackways are interpreted as produced by theropods, two large and one smaller. In these beds there are also ostracods, spinicaudatans (conchostracans), and fragments of microvertebrates (fish scales, teeth and bones). The Sitio Pereiros ichnosite represents a deposition in a floodplain area, with temporary aerial exposure of the superficial sediments in which tracks were impressed. The ichnofauna from this locality increases knowledge of the theropod fauna from the Triunfo basin and the distribution of the dinosaur tracks throughout the interior basins of Northeastern Brazil. Description of these new theropod tracks permits evaluation of the behavior of these three theropods, including inferences about trackmaker speed and the type of gait of the three animals, and also of their possible size. This is the 40th ichnosite in the Rio do Peixe basins, extending analysis of the types of trackmaker associations present at such ichnosites, as well as the dinosaur diversity represented at each of them. New interpretations are presented about the environments, and the relationship between the various groups represented in this region during the Early Cretaceous. (c) 2022 Elsevier Ltd. All rights reserved.