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Basal dinosaur I



THE FIRST CERATOSAURIA (?COELOPHYSOIDEA) DINOSAUR FROM SANTA MARIA FORMATION, TRIASSIC OF RIO GRANDE DO SUL STATE, BRAZIL

FERIGOLO, J.
RIBEIRO, A. M.
RAIMUNDO-SILVA, R.
CABREIRA, S. F.

Material from Dona Francisca County consists of associated, partially disarticulated individuals, including three skulls and postcranial portions, as well as isolated skull/mandible fragments. Although most of material is still to be prepared, some characters can be observed: skulls are long (~30cm), low and narrow, with very long antorbital fenestra; serrated teeth; interdental plates; astragalus/calcaneum fused each other; large and vertically directed astragalar ascending process; femur (~18cm) longer than tibia (~14cm). Some these characters suggest a Coelophysoidea ceratosaur, a group not reported previously for South America. The presence of large size "thecodonts" (?Prestosuchus) the traversodontid (?Massetognathus) and medium size dicynodnts (? Dinodontosaurus), as well the absence of Upper Triassic vertebrates, permit to infer a Middle Triassic (?Ladinian) age for stratigraphic levels of ceratosaur material. These findings partially corroborate the hypothesis that the divergence between Ceratosauria and Tetanurae occurred before Upper Triassic. However the presence of a typical Ceratosauria in the Middle Triassic (?Ladinian) permit to suppose that such divergence could be have occurred at the Anisian or even before.

Ferigolo, J.; Ribeiro, A. M.; Raimundo-Silva, R.; & Cabreira, S. The first Ceratosauria (?Coleophysoidea) Dinosaur from Santa Maria Formation, Triassic of Rio Grande do Sul State, Brazil. In: JORNADAS ARGENTINAS DE PALEONTOLOGIA DE VERTEBRADOS, 17. Esquel - Chubut. 2001. Resumenes... Esquel - Chubut, p. 13.