Adamantisaurus, meaning “Adamantina lizard”, is a genus of titanosaurian sauropod dinosaur from the Turonian-Maastrichtian stages of the Late Cretaceous Period (93 to 70 million years ago). It lived in what is now South America. It was discovered in the Adamantina Formation in the Bauru Group of geologic formations.
The remains of Adamantisaurus were first mentioned in 1959, but the dinosaur was not named until 2006 by Brazilian paleontologists Rodrigo Santucci and Reinaldo Bertini. It was the first dinosaur named that year. The type species (A. mezzalirai) was named in honor of Sergio Mezzalira, the paleontologist who found the remains and first mentioned it.
Adamantisaurus is only known from six tail vertebrae, but it is assumed that it was a very large dinosaur with a long neck and tail. It may have been armored, but with lack of further evidence, its exact appearance will remain a mystery. Where there is little fossil material, it is also difficult to determine the exact placement and relationship of the Adamantisaurus to other dinosaurs. Some similarities have been noted with Aeolosaurus and Trigonosaurus.