| Ibirania | |
|---|---|
.jpg) | |
| Caudal vertebra (left) and ulna (right) ofIbirania | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Clade: | †Macronaria |
| Clade: | †Titanosauria |
| Family: | †Saltasauridae |
| Subfamily: | †Saltasaurinae |
| Genus: | †Ibirania Navarro et al.,2022 |
| Type species | |
| †Ibirania parva Navarro et al., 2022 | |
Ibirania (meaning "Ibirá wanderer" or "tree wanderer") is a genus of dwarfsaltasaurinetitanosaur dinosaur from theLate Cretaceous (Santonian toCampanian)São José do Rio Preto Formation (Bauru Basin) of Southeast Brazil. The type species isIbirania parva.[1] It is one of the smallest sauropods known to date, comparable in size to the titanosaurMagyarosaurus.[2]
TheIbiraniaholotype specimen, LPP-PV-0200–0207, was discovered in layers of the São José do Rio Preto Formation on the Garcia Brothers Farm inVila Ventura,Ibirá Municipality, northeasternSão Paulo State,Brazil, which dates to the lateSantonian to earlyCampanian ages of the late Cretaceous period. The holotype consists of adorsal vertebra, partialcaudal vertebrae, a fragmentaryradius andulna, a partialmetacarpal, and a nearly completemetatarsal. Additional material, including partialcervical, dorsal, and caudal vertebrae, fragments of a fibula, and a nearly complete fibula, was also referred toIbirania.[1]
In 2022, Navarro et al.describedIbirania as a new genus and species of saltasaurine titanosaur. Thegeneric name, "Ibirania", combines a reference toIbirá, the municipality where the specimens were discovered (also aPortuguese derivative of theTupi word "ybyrá", meaning "tree", in reference toIbirania's hypothesized browsing behavior), with "ania", a modified form of theGreek word "plania", meaning "wanderer". Thespecific name, "parva", is derived from theLatin word "parvus", meaning "small", afternanism 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 computedtomography, Aureliano et al. (2021) discovered highly pneumatized vertebrae in theIbirania holotype. Despite the nanoid status ofIbirania, 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 ofpneumosteum throughout the internaltrabeculae, definitive evidence of the preterit interaction of a bird-likeair sac system in the bone.[3]
One of the specimens ofIbirania (LPP-PV-0043, a partial fibula) presented apathology called acuteosteomyelitis. Aureliano et al. (2021) sampled histological thin sections of the lesion and described the step-by-step development ofperiosteal remodeling caused by the infection. They also usedCT 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 inIbirania (LPP-PV-0043). It was the first report of parasites preservedin 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 was a derived member of theSaltasaurinae, a clade known for encompassing some of the smallest titanosaurs.Ibirania was recovered as sister taxa of the clade formed by the Patagonian saltasaurinesBonatitan andRocasaurus.
Thecladogram below displays the results of thephylogenetic analyses performed by Navarro et al. (2022):[1]
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 asEuropasaurus andMagyarosaurus, which attained their small size due toinsular dwarfism.[1]
It coexisted alongside other dinosaurs, such as theabelisaurid theropodThanos simonattoi and a larger, unnamed probablemegaraptoran,[5] as well as an indeterminatenotosuchian.[6][7]
