A new desert-dwelling dinosaur (Theropoda, Noasaurinae) from the Cretaceous of south Brazil

LANGER, MAX CARDOSO; MARTINS, NEURIDES DE OLIVEIRA; MANZIG, PAULO CÉSAR; FERREIRA, GABRIEL DE SOUZA; MARSOLA, JÚLIO CÉSAR DE ALMEIDA; FORTES, EDISON; LIMA, ROSANA; SANT?ANA, LUCAS CESAR FREDIANI; VIDAL, LUCIANO DA SILVA; LORENÇATO, ROSANGELA HONÓRIO DA SILVA; EZCURRA, MARTÍN DANIEL

Scientific Reports

Springer

Año: 2019 vol. 9

Noasaurines form an enigmatic group of small-bodied predatory theropod dinosaurs known fromthe Late Cretaceous of Gondwana. They are relatively rare, with notable records in Argentina andMadagascar, and possible remains reported for Brazil, India, and continental Africa. In south-centralBrazil, the deposits of the Bauru Basin have yielded a rich tetrapod fauna, which is concentrated in theBauru Group. The mainly aeolian deposits of the Caiuá Group, on the contrary, bear a scarce fossil recordcomposed only of lizards, turtles, and pterosaurs. Here, we describe the first dinosaur of the CaiuáGroup, which also represents the best-preserved theropod of the entire Bauru Basin known to date.The recovered skeletal parts (vertebrae, girdles, limbs, and scarce cranial elements) show that the newtaxon was just over 1 m long, with a unique anatomy among theropods. The shafts of its metatarsalsII and IV are very lateromedially compressed, as are the blade-like ungual phalanges of the respectivedigits. This implies that the new taxon could have been functionally monodactyl, with a main centralweight-bearing digit, flanked by neighbouring elements positioned very close to digit III or even heldfree of the ground. Such anatomical adaptation is formerly unrecorded among archosaurs, but hasbeen previously inferred from footprints of the same stratigraphic unit that yielded the new dinosaur. Aphylogenetic analysis nests the new taxon within the Noasaurinae clade, which is unresolved becauseof the multiple alternative positions that Noasaurus leali can acquire in the optimal trees. The exclusionof the latter form results in positioning the new dinosaur as the sister-taxon of the ArgentineanVelocisaurus unicus.