Adamantinasuchus is an extinct genus of notosuchian crocodylomorph from and named after the Late Cretaceous Adamantina Formation of Brazil.

The fossil consists of a partial skull, fragmentary limb bones and a few broken vertebrae, and was found 25 kilometres (16 mi) southwest of the town of Marilia, near a reservoir dam.

The maxilla itself is mostly triangular, with a long anteroposterior base at the ventral side of which is a thin crest that covers the border of the dental alveoli.

Towards the posterior end the maxilla is elongated, and it forms a long suture with the jugal beneath the large orbits.

[1] The nasal bone is very incompletely preserved; what there is curves around ventrally, and is slightly sculptured towards the anterior end.

The prefrontal's outer surface is very smooth, possibly due to contact with a palpebral bone (not preserved).

Its outer surface is smooth and there is a large foramen in the anterior section of the bone, close to the very thin crest in the medial portion that comes to a slender edge.

The jugal is arched medially, curving out laterally away from the orbit, and is widest just behind the long suture with the maxilla, tapering to a bladelike portion at the posterior end.

The mandibular fenestra is elliptical, and does not excavate the dentary noticeably, rather remaining between angular and surangular.

The third premaxillary tooth is caniniform and is much larger than the incisiform teeth, though it is a similar conical shape.

There is insufficient preservation of the quadrate or the articular bones to tell whether its jaw was capable of back-and-forth movements necessary for chewing plants, but the relative lack of wear on its molariform teeth suggest that it was probably only capable of dorsoventral biting motions, not chewing, and that it mainly ate softer food than plants.

[1] Below is a cladogram modified from O’Connor et al., 2010: Uruguaysuchus Libycosuchus Malawisuchus Candidodon Mariliasuchus Pakasuchus Adamantinasuchus Simosuchus Notosuchus Chimaerasuchus Sphagesaurus Comahuesuchus Baurusuchus