First evidence of an unenlagiid (Dinosauria, Theropoda, Maniraptora) from the Bauru Group, Brazil

Abstract

In this study, we describe a small theropod dorsal vertebra from the Late Cretaceous Bauru Group (Brazil). The specimen is referred to the maniraptoran clade Unenlagiidae based on the following combination of characters: diapophyses short, wide and weakly inclined; dorsal surface of the neural spine transversely expanded; neural spine at least twice as high than it is long at mid-height; and deep lateral excavations of the ventrolateral surface of the neural spine. The vertebra belonged to an ontogenetically mature individual with an estimate total body length of around 1 m. This is the first evidence of Unenlagiidae in Brazil, a clade currently known only from Argentina and possibly Madagascar. The presence of large- to small-bodied forms in the TuronianeSantonian of South America indicates that Unenlagiinae were ecologically disparate during the first half of the Cretaceous. The Bauru vertebra shows a combination of avian-like, Rahonavis-like and Unenlagia-like features, making it a possible pivotal taxon in future phylogenetic investigations of intra- and interrelationships of unenlagiids.