Caiuajara is an extinct genus of tapejarid pterosaur from the Early Cretaceous period (Aptian to Albian stages) of Brazil.

[4] The holotype, CP.V 1449, was found in a sandstone layer of the Goio-Erê Formation, of Early Cretaceous age,[5] in the Paraná Basin.

[6] It consists of a partial skeleton including the skull, lower jaws, neck vertebrae and wing elements.

The species had a large toothless head with, in adult individuals, an enormous shark fin-shaped crest on the snout.

The rear ascending branches of the premaxillae on their midline form an elongated bony rim projecting to below into the nasoantorbital fenestra, the large skull opening in the side of the snout.

In the concave upper rear of the symphysis, the fronts of the lower jaws grown together, a rounded depression is present.

[7] Azhdarchidae Chaoyangopteridae Keresdrakon vilsoni Thalassodromeus sethi Tupuxuara leonardii Caupedactylus ybaka Aymberedactylus cearensis Eopteranodon lii "Huaxiapterus" benxiensis "Huaxiapterus" corollatus Sinopterus dongi Europejara olcadesorum Caiuajara dobruskii Tapejara wellnhoferi Tupandactylus imperator The habitat of Caiuajara was a desert with dunes.

[4] The large concentrations of fossils, among pterosaurs very rare and only equaled by those found of the Argentine form Pterodaustro, were by the describers seen as proof of a gregarious lifestyle, Caiuajara living in colonies.

The many specimens also allowed to determine a growth series, the first such an ontogenetic sequence for pterosaurs of which it is nearly certain that it really represented a single species.

The age of the exemplars can be determined, not just from size but also by the degree of ossification, especially of the breastbone, the long bones and the wrist, and the fusion of the shoulder blade and coracoid into a scapulocoracoid.

No specimens have been found lacking the snout crest, indicating that Caiuajara was in this respect not sexually dimorphic and casting doubt on the hypothesis that pterosaurs normally were.