A new Unenlagiinae (Theropoda: Dromaeosauridae) from the Late 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 undoubtful nominal unenlagiine
dromaeosaurid species from Brazil, from the Marília Formation
(Maastrichtian), Bauru Group, Paraná Basin. The specimen comprises a
partial right maxilla (with three teeth in loci) and a right dentary.
Ypupiara is characterized by the morphology of the maxilla, presenting
restrict number of neurovascular foramina on lateral surface, rectangular
and anteroposteriorly expanded interdental plate, teeth with labiolingual
diameter more than 3/5 of the rostrocaudal diameter, teeth widely spaced
and labiolingually compressed. Our phylogenetic analysis recovers Ypupiara
as an unenlagiine based on fluted teeth, and places it as the sister taxon
of Austroraptor cabazai due to the ratio between the labiolingual and
mediodistal diameters of the teeth more than 3/5. We also erect the new
group Unenlagiinia, which includes Unenlagiinae and Halszkaraptorinae
clades. Ypupiara nests within this new group based on widely spaced teeth
and the lack of mesial/distal carinae in maxillary teeth. The morphology
of the teeth is similar to Buitreraptor gonzalezorum, although the
proportions are markedly distinct. The teeth and comparisons with other
Unenlagiinia also support that fish was part of the diet for Ypupiara. We
also performed a Parsimony Analisys of Endemicity, which suggests that the
presence of unenlagiines in Brazilian Upper Cretaceous outcrops is
explained by dispersion or extinct events. The new species provides new
information on the evolution of Gondwanan dromaeosaurids, and its
preserved teeth provides new data to assign isolated dromaeosaurid teeth
from Bauru Group.