Biogeography of theropod dinosaurs during the Late Cretaceous: evidence from central South America

In central South America, theropod remains are relatively scarce in comparison to the southern part of the continent, with shed teeth being the primary fossils found in this region. We examined 179 isolated teeth from the Bauru Basin, Brazil, using linear discriminant analysis (LDA; N = 178) and phylogenetic analysis (N = 174). The LDA used eight measurements, and the phylogenetic analysis used seven morphotypes. Although the results of the LDA suggest the presence of various South American theropod clades, such as Carcharodontosauridae, Noasauridae, and Spinosauridae, the phylogenetic analysis using a constrained dentition-based matrix classified the morphotypes as Abelisauridae (morphotypes I-IV, VI, and VII) and Therizinosauria (morphotype V). Given the considerable number of homoplastic characters and missing data, the phylogenetic analyses could not precisely determine the taxonomy of morphotypes V, VI, and VII in the unconstrained dataset. Morphological comparisons, nevertheless, strongly suggest that all morphotypes should be classified as abelisaurid theropods. We propose that the palaeogeographical distribution of Abelisauridae in South America was influenced by climatic conditions. These apex carnivores are likely to have adapted well to increased climate changes that led to semi-arid conditions. Our research sheds light on the evolutionary and ecological aspects of theropod dinosaurs in this region, contributing to a better understanding of the ancient ecosystems of central South America.