Ibirania

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Ibirania
Temporal range: Late Cretaceous (Santonian–Campanian)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
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 "

Southeast Brazil. The type species is Ibirania parva.[1] It is one of the smallest sauropods known to date, comparable in size to the titanosaur Magyarosaurus.[2]

Discovery and naming

The Ibirania

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.

nanism seen in the taxon. The intended name meaning is "little Ibirá wanderer" or "little tree wanderer".[1]

Description

Size of Ibirania compared to a human

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]

Classification

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.

The cladogram below displays the results of the phylogenetic analyses performed by Navarro et al. (2022):[1]

Paleopathology

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]

Paleoparasitology

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]

Paleoenvironment

Life restoration
of Ibirania

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]

It coexisted alongside other dinosaurs, such as the

abelisaurid theropod Thanos simonattoi and a larger, unnamed probable megaraptoran,[5] as well as an indeterminate notosuchian.[6][7]

References

  1. ^
    S2CID 251875979
    .
  2. ISBN 978-0-691-16766-4
    .
  3. PMID 34921226
    .
  4. ^
    S2CID 225134198
    .
  5. S2CID 92754354
    .
  6. doi:10.1016/j.cretres.2009.07.003
    .
  7. S2CID 238725546
    .
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