Basal dinosaur I

[Hebert Bruno Campos <hebertcampos@bol.com.br>]

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.