THE RECORD OF THEROPODA (DINOSAURIA) BASED ON DENTAL CROWNS FROM UPPER CRETACEOUS OF BRAZIL (BAURU GROUP AND CAMBAMBE UNIT)

The record of Brazilian theropod is still scarce considering the surface of the country. Nevertheless, the Bauru Group (Upper Cretaceous, Bauru Basin) represents an important geological unit where are unearthed remains of dinosaur, crocodile, bird, mammal, squamate and amphibian fossils. Even in Bauru Group, theropods are very fragmented with only one species recognized, but with a large record of dental crowns. Here we assessed the ecology and taxonomy of the crowns using linear morphometric tools. We have taken measurements of 170 crowns adding those in a published matrix resulting in a database with 1176 theropod dental crowns. These crowns were from Marília, Adamantina, Presidente Prudente formations and Cambambe unit ("Parecis Group"). This last one was chosen due to the chrono-geological similarities with Bauru Group. The measurements used are the crown base length, width and height; distocentral and mesiocentral denticle density; mid-crown length and width. We performed PCA and LDA analyses for ecological and taxonomic approaches respectively. To reduce noise in the LDA analysis, we excluded all non-Creataceous and non-South America taxa, resulting in a reduced dataset with 747 crowns. In the PCA conducted with the full dataset, 93.73% of the variance is explained by PC1, while 4.8% is explained by PC2. The results suggest that theropod from Bauru Group were ecological diverse occupying roles as small to large predators, such as abelisaurids, neovenatorids, carcharodontosaurids and tyrannosaurids. The role of small predators is less evident among the crows and are shared mainly by maniraptorans, and with small nosaurids. The LDA analysis recovered the Bauru's crowns mainly among abelisaurids and dromaeosaurids. Some crowns were recovered among carcharodontosaurids and spinosaurids. However, it is important to note that the morphometric analyses are not good enough to taxonomic purposes; and, although some crowns have similar metrics with these two groups, they were extinct during Campanian-Maastrichtian (Bauru and "Parecis" groups age). Therefore, more analyses are necessary before any taxonomic conclusion. The humble number of small theropods recovered in the PCA analysis suggests that they could share niche with other group of carnivores (i.e. crocodiles). We are still analyzing the data with more tests coming. [CAPES 88882.305879/2018-01]