A NEW EARLY LATE TRIASSIC SAURISCHIAN DINOSAUR FROM RIO GRANDE DO SUL STATE, BRAZIL
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Two incomplete specimens of a new genus and species of Saurischia, Guaibasaurus candelariensis, from the Caturrita Formation of Rio Grande do Sul, southern Brazil, offers new data on the basal dinosaurs and a new interpretation of the early evolution of the Saurischia. The new taxon is more primitive than the Herrerasauridae, in the structure of the dorsal vertebrae, ilium, pubis, femur, tarsus and foot. The mesotarsal condition and the outline of the distal section of tibia indicate the saurischian nature of this new form, but the almost unreduced medial wall of the acetabular portion of ilium shows an unrecorded primitive condition within the cited group. These particular characters lead us to propose a new family : the Guaibasauridae. Several features suggesting affinities with both the Prosauropoda and Theropoda, imply that Guaibasaurus candelariensis may belong to the ancestral group for both of them.