A theropod tooth from the Missão Velha Formation (Late Jurassic-Early Cretaceous) of the Araripe Basin: oldest Brazilian Abelisaurid record

The Missão Velha Formation (Late Jurassic-Early Cretaceous), often referred to as Brejo Santo Formation, is one of the stratigraphic units of the Araripe Basin, included within the Vale do Cariri Group. This locality, characterised by its fluvio-estuarine paleoenvironment, yielded a diverse paleoichthyofauna while its terrestrial vertebrate record is still poorly known, with a single isolated theropod lateral tooth being briefly cited until now. This study aims to revisit this specimen (UERJ-PMB R008) in order to identify it through the current quantitative and qualitative methods. The quantitative analyses were unable to properly classify the Missão Velha specimen to a single theropod group, indicating paravian, piatnitzkysaurid and abelisaurid affinities, while most of cladistic analyses assigned the UERJ-PMB R008 as an abelisaurid tooth. The specimen was finally assigned as an abelisaurid lateral tooth due to its almost straight distal margin, hooked denticles, similarly sized mesial and distal denticles, a lanceolate cross section and an irregular enamel texture. This assignment represents not only the first definitive theropod record for Missão Velha Formation as it is also the oldest abelisaurid record in the South America, filling part of the 30-million-year gap between <i>Eoabelisaurus</i> and <i>Spectrovenator</i>.