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Basal dinosaur I
THE FIRST CERATOSAURIA (?COELOPHYSOIDEA) DINOSAUR FROM SANTA MARIA
FORMATION, TRIASSIC OF RIO GRANDE DO SUL STATE, BRAZIL
RIBEIRO, A. M.
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.