the south of Brazil. A phylogenetic analysis conducted in 2019 by Kellner (one of the describers of Caiuajara) and colleagues recovered Caiuajara within the tribe Tapejarini, sister taxon to sister taxon to three other genera: Europejara, Tapejara, and Tupandactylus. Paleobiology The habitat of Caiuajara was a desert with dunes. The layers in which the fossils were found had been deposited in a lake in the desert; probably the bones had been exposed at the surface around the lake for a time and were then by storms blown into it, eventually sinking to the bottom. Possibly the same storms caused many individuals to die together; this could also have been the result of droughts. A succession of layers shows that the lake was likely inhabited by the pterosaurs for a great length of time, although it is also possible they visited the lake during regular migrations. Fossil plants — tapejarids are often assumed to have been herbivores — have not been found, so there are no direct indications about the food source. Likewise, remains of invertebrates have not been discovered. 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. It showed that juvenile individuals, the smallest specimens of which have a wingspan of about , generally had the same proportions as adults. Especially important is that their humeri are not proportionally smaller and their humeral deltopectoral crests, the attachments of the main flight muscles, are not less developed, attaining a size of 38 to 40% of the humeral shaft length. This suggests that they were precocial, taking wing almost as soon as they hatched; parental care must have been limited. This might have been typical of all derived pterosaurs. The snout crest however, strongly changed during growth. It became much taller and also much more steeply inclined, from about 115° to 90°. Although