A New Unenlagiine (Theropoda, Dromaeosauridae) From The Upper Cretaceous Of Brazil

The record of unenlagiines in Brazil, except for one dorsal vertebra, is still under debate based on isolated teeth. Here, we describe Ypupiara lopai gen. et sp. nov., the first dromaeosaurid species from Brazil, from the Maastrichtian of the Bauru Group, Parana Basin. The specimen consists of a partial right maxilla (with three teeth in loci) and a right dentary. Ypupiara is characterized by a restricted number of neurovascular foramina on the lateral surface of the maxilla, a rectangular and anteroposteriorly expanded interdental plate, and a labiolingual compression of the teeth, which have a labiolingual diameter more than 3/5 of the rostrocaudal diameter. Our phylogenetic analysis recovers Ypupiara as an unenlagiine based on the fluted teeth and places it as the sister taxon of Austroraptor due to the ratio of the labiolingual and mesiodistal diameters of the teeth being more than 3/5. We also erect the new group Unenlagiinia, which includes Unenlagiinae and Halszkaraptorinae. Ypupiara nests within Unenlagiinia based on the widely spaced teeth and the lack of mesial and distal carinae in the maxillary teeth. The morphology of the teeth is similar to Buitreraptor, although the proportions are markedly distinct. The teeth and comparisons with other Unenlagiinia also support fish being part of the diet for Ypupiara. We also performed a parsimony analysis of endemicity, which suggested that the presence of unenlagiines in Brazilian Upper Cretaceous outcrops is explained by dispersion or extinction events. The new species provides new information on the evolution of Gondwanan dromaeosaurids, and its preserved teeth provide new data to enable the assignment of isolated dromaeosaurid teeth from the Bauru Group.