Introducing Ypupiara lopai

Restoration of two individuals of Ypupiara lopai. Credit: Guilherme Gehr

The iconic Velociraptor mongoliensis, described by Osborn in 1924, belongs to the Dromaeosauridae, a family of highly derived small to mid-sized theropod dinosaurs closely related to birds. Their fossils have been found in North America, Europe, Africa, Asia, South America and Antarctica. The group is characterized by the presence of long, three-fingered forelimbs that ended in sharp, trenchant claws, and a tail stiffened by the elongated prezygapophyses. In Gondwana, the clade Unenlagiinae is a diversification of dromaeosaurids. The group includes Buitreraptor and Austroraptor from Argentina. Ypupiara lopai from the Maastrichtian of the Bauru Group is the first unenlagiine dromaeosaurid species from Brazil.

The holotype (DGM 921-R) includes a partial preantorbital portion of a right maxillary, with three teeth in loci, and a partial posterior portion of a right dentary. The generic name means ‘the one who lives in the water’, an allusion to a Tupian myth about an aquatic creature. The specific name honors Alberto Lopa, the holotype’s discoverer. Ypupiara was found between the 40s and 60s in Peirópolis, near Uberaba, and placed in storage at the National Museum of Brazil. Unfortunately, the fossil was lost when the museum was consumed by a fire on 2 September 2018, but photographs of the specimen survived.

Right maxilla of DGM 921-R with details of teeth. Scale bar: 10 mm. From Brum et al., 2021.

Ypupiara is characterized by the morphology of the maxilla that exhibits a restrict number of neurovascular foramina on lateral surface, rectangular and anteroposteriorly expanded interdental plate, and teeth widely spaced and labiolingually compressed. Based on the ratio between the labiolingual and mediodistal diameters of the teeth more than 3/5, Ypupiara was classified as a sister-group of A. cabazai. It was suggested that unenlagiines consumed fish at least as part of their diet and potentially as the main source of food at least in Austroraptor due to its conidont dentition.

 

References:

Brum, Arthur Souza, Pêgas, Rodrigo Vargas, Bandeira, Kamila Luisa Nogueira, Souza, Lucy Gomes de, Campos, Diogenes de Almeida, & Kellner, Alexander Wilhelm Armin. (2021). A new Unenlagiinae (Theropoda: Dromaeosauridae) from the Late Cretaceous of Brazil. https://doi.org/10.1002/spp2.1375

Gianechini, Federico A and S. Apesteguía. (2011) “Unenlagiinae revisited: dromaeosaurid theropods from South America.” Anais da Academia Brasileira de Ciencias 83 1: 163-95 .

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