Saturnalia tupiniquim

Saturnalia is an extinct genus of basal prosauropod  dinosaur from the Triassic of Rio Grande do Sul, southern Brazil. The deposits are dated to the early Upper Triassic, about 225 million years ago (mya). The dinosaur grew to about 1.5 meters (5 ft) long.

Phylogeny
Saturnalia is primitive, and its mixture of characteristics,"basal sauropodomorph" and "prosauropod" mean the same thing. has made it difficult to classify. It is one of the oldest true dinosaurs yet found.

The first (1999) description of the genus assigned it to the Sauropodomorpha.Langer M.C; Abdala F; Richter M. and Benton M. 1999. A sauropodomorph dinosaur from the Upper Triassic (Carnian) of southern Brazil. Comptes Rendus de l'Académie des Sciences, 329: 511-517. However, in a 2003 paper, Langer noted that features of its skull and hand were more similar to the sister group of sauropodomorphs, the theropods. Also that Saturnalia could be a member of the sauropodomorph "stem-lineage", rather than a true member of that group.Langer M.C. 2003. The pelvic and hind limb anatomy of the stem-sauropodomorph Saturnalia tupiniquim (late Triassic, Brazil). PaleoBios, 23(2). 

José Bonaparte and colleagues, in a 2007 study, found Saturnalia to be very similar to the primitive saurischian Guaibasaurus. Bonaparte placed the two in the same family, Guaibasauridae. Like Langer, Bonaparte found that these forms may have been primitive sauropodomorphs, or an assemblage of forms close to the common ancestor of the sauropodomorphs and theropods. Overall, Bonaparte found that both Saturnalia and Guaibasaurus were more theropod-like than prosauropod-like.Bonaparte J.F. et al 2007. A new specimen of Guaibasaurus candelariensis (basal Saurischia) from the late Triassic Caturrita Formation of southern Brazil. Historical Biology, 19(1): 73-82. 

However, all more recent cladistic analyses found it to be a very basal sauropodomorph,

References

Category:Dinosaurs of South America
Category:Triassic dinosaurs