The Ibiraniaholotype specimen, LPP-PV-0200–0207, was discovered in layers of the São José do Rio Preto Formation on the Garcia Brothers Farm in Vila Ventura, Ibirá Municipality, northeastern São Paulo State, Brazil, which dates to the late Santonian to early Campanian ages of the late Cretaceous period. The holotype consists of a dorsal vertebra, partial caudal vertebrae, a fragmentary radius and ulna, a partial metacarpal, and a nearly complete metatarsal. Additional material, including partial cervical, dorsal, and caudal vertebrae, fragments of a fibula, and a nearly complete fibula, was also referred to Ibirania.[1]
In 2022, Navarro et al. describedIbirania as a new genus and species of saltasaurine titanosaur. The generic name, "Ibirania", combines a reference to Ibirá, the municipality where the specimens were discovered (also a Portuguese derivative of the Tupi word "ybyrá", meaning "tree", in reference to Ibirania's hypothesized browsing behavior), with "ania", a modified form of the Greek word "plania", meaning "wanderer". The specific name, "parva", is derived from the Latin word "parvus", meaning "small", after nanism seen in the taxon. The intended name meaning is『little Ibirá wanderer』or "little tree wanderer".[1]
Ibirania is estimated to be only 5.7 metres (19 ft) long, making it one of the smallest sauropods.[1]
Using computed tomography, Aureliano et al. (2021) discovered highly pneumatized vertebrae in the Ibirania holotype. Despite the nanoid status of Ibirania, the extreme pneumatization of its axial skeleton was inherited from its giant titanosaurian relatives. The histological thin sections of the vertebral bone revealed the preservation of pneumosteum throughout the internal trabeculae, definitive evidence of the preterit interaction of a bird-like air sac system in the bone.[3]
Ibirania was a derived member of the Saltasaurinae, a clade known for encompassing some of the smallest titanosaurs. Ibirania was recovered as sister taxa of the clade formed by the Patagonian saltasaurines Bonatitan and Rocasaurus.
One of the specimens of Ibirania (LPP-PV-0043, a partial fibula) presented a pathology called acute osteomyelitis. Aureliano et al. (2021) sampled histological thin sections of the lesion and described the step-by-step development of periosteal remodeling caused by the infection. They also used CT scan slices and a reconstructed 3D model to describe the trauma.[4]
Aureliano et al. (2021) also discovered fossilized parasites associated with the bone lesions in Ibirania (LPP-PV-0043). It was the first report of parasites preserved in situ inside the vascular canals of a dinosaur. The taxonomy of these microfossils are currently under study by the rest of the team.[4]
Ibirania lived in an arid, inland environment, which Navarro et al. (2022) presume is the reason behind its dwarfism.[1] This is in contrast to other dwarf sauropods such as Europasaurus and Magyarosaurus, which attained their small size due to insular dwarfism.[1]
^Delcourt, Rafael; Vidoi Iori, Fabiano (2020). "A new Abelisauridae (Dinosauria: Theropoda) from São José do Rio Preto Formation, Upper Cretaceous of Brazil and comments on the Bauru Group fauna". Historical Biology. 32 (7): 917–924. Bibcode:2020HBio...32..917D. doi:10.1080/08912963.2018.1546700. S2CID92754354.
^Montefeltro, F.C.; Laurini, C.R.; Langer, M.C. (2009). "Multicusped crocodyliform teeth from the Upper Cretaceous (São José do Rio Preto Formation, Bauru Group) of São Paulo, Brazil". Cretaceous Research. 30 (5): 1279–1286. Bibcode:2009CrRes..30.1279M. doi:10.1016/j.cretres.2009.07.003.
^Marinho, Thiago S.; Martinelli, Agustín G.; Basilici, Giorgio; Soares, Marcus Vinícius T.; Marconato, André; Ribeiro, Luiz C. B.; Iori, Fabiano V. (2022). "First Upper Cretaceous notosuchians (Crocodyliformes) from the Uberaba Formation (Bauru Group), southeastern Brazil: Enhancing crocodyliform diversity". Cretaceous Research. 129: 105000. Bibcode:2022CrRes.12905000M. doi:10.1016/j.cretres.2021.105000. ISSN0195-6671. S2CID238725546.
