Trigonosaurus (meaning "triangle lizard" after Triangulo Mineiro, where it was found[1]), is a genus of saltasaurid dinosaurs from the Maastrichtian Serra da Galga Formation of Brazil.

[1] From the 1940s to 1960s, Brazilian paleontologist Llewellyn Ivor Price excavated several series of titanosaur fossils in the "Caieira" locality of the Serra da Galga Formation in Minas Gerais, Brazil.

[1] Further titanosaur fossils from the BR-262 site of the same locality were reported by Silva Junior and colleagues in 2022, and in light of this new evidence, reconsidered MCT 1488-R to be a specimen of Baurutitan, thus synonymizing Trigonosaurus with it.

They also separated the caudal vertebrae (paratype) from Trigonosaurus and described it as the holotype of a new genus and species of titanosaur, Caieiria allocaudata.

[2] However, not all researchers have accepted the conclusion that Trigonosaurus is a synonym of Baurutitan; John Fronimos, in 2023, did not follow the proposed synonymy due to the differencess between the first caudal vertebrae of the two taxa.