Friday, February 15, 2019

[Paleontology • 2019] Nhandumirim waldsangae • A New Dinosaur with Theropod Affinities from the Late Triassic Santa Maria Formation, South Brazil

Nhandumirim waldsangae 

Marsola, Bittencourt, Butler, Da Rosa, Sayão & Langer, 2019

The Late Triassic (Carnian) upper Santa Maria Formation of south Brazil has yielded some of the oldest unequivocal records of dinosaurs. Here, we describe a new saurischian dinosaur from this formation, Nhandumirim waldsangae, gen. et sp. nov., based on a semiarticulated skeleton, including trunk, sacral, and caudal vertebrae, one chevron, right ilium, femur, partial tibia, fibula, and metatarsals II and IV, as well as ungual and non-ungual phalanges. The new taxon differs from all other Carnian dinosauromorphs through a unique combination of characters, some of which are autapomorphic: caudal centra with sharp longitudinal ventral keels; brevis fossa extending for less than three-quarters of the ventral surface of the postacetabular ala of the ilium; dorsolateral trochanter ending well distal to the level of the femoral head; distal part of the tibia with a mediolaterally extending tuberosity on its cranial surface and a tabular caudolateral flange; conspicuous, craniomedially oriented semicircular articular facet on the distal fibula; and a straight metatarsal IV. This clearly distinguishes Nhandumirim waldsangae from both Saturnalia tupiniquim and Staurikosaurus pricei, which were collected nearby and at a similar stratigraphic level. Despite not being fully grown, the differences between Nhandumirim waldsangae and those saurischians cannot be attributed to ontogeny. The phylogenetic position of Nhandumirim waldsangae suggests that it represents one of the earliest members of Theropoda. Nhandumirim waldsangae shows that some typical theropod characters were already present early in dinosaur evolution, and it represents possibly the oldest record of the group known in Brazil.

  Silhouette depicting the preserved bones of Nhandumirim waldsangae, gen. et sp. nov. (LPRP/USP 0651).


DINOSAURIFORMES Novas, 1992, sensu Nesbitt, 2011 
DINOSAURIA Owen, 1842, sensu Padian and May, 1993 

SAURISCHIA Seeley, 1887, sensu Gauthier, 1986 
cf. THEROPODA Marsh, 1881, sensu Gauthier, 1986 


Etymology— The generic name combines the Portuguese derivatives of the indigenous Tupi-Guarani words ‘Nhandu’ (running bird, common rhea) and ‘Mirim’ (small), in reference to the size and inferred cursorial habits of the new dinosaur. The specific epithet name refers to the Waldsanga site, the historic outcrop (Langer, 2005a) that yielded this new species.

Júlio C. A. Marsola, Jonathas S. Bittencourt, Richard J. Butler, Átila A. S. Da Rosa, Juliana M. Sayão and Max C. Langer. 2019. A New Dinosaur with Theropod Affinities from the Late Triassic Santa Maria Formation, South Brazil. Journal of Vertebrate Paleontology. e1531878 DOI: 10.1080/02724634.2018.1531878   

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