Open Paleo

Parankylosauria

Soto-Acuña et al., 2021

Its genera lived 113.2–66.0 million years ago Early Cretaceous–Late Cretaceous
Early Cretaceous and Late Cretaceous stages

Parankylosauria is an early-diverging clade of armored dinosaurs that lived across the former southern supercontinent of Gondwana — in what are now South America, Antarctica, and Australia — during the Cretaceous. It is recovered as the first lineage to branch off from the rest of the ankylosaurs, making it the sister group to Euankylosauria, the ankylosaurids and nodosaurids that dominate the Northern Hemisphere. Its members, including Stegouros, Antarctopelta, and Kunbarrasaurus, were relatively small, roughly 1.5 to 4 meters long, and retained a number of primitive traits shared with early armored dinosaurs and stegosaurs but lost in other ankylosaurs, such as longer, more slender limbs and simple, narrow hips. Their skulls bear elongate snouts with distinctive narrow nasal bones and lack the elaborate horns and bosses seen in other ankylosaurs. Rather than a knob-like tail club, several parankylosaurs carried a frond-like tail weapon known as a macuahuitl, formed from flattened osteoderms arranged along both sides of the tail.

Under dispute

The monophyly of Parankylosauria is contested. Soto-Acuña and colleagues (2021) erected it for Stegouros, Antarctopelta, and Kunbarrasaurus and recovered it across five matrices, with support from Soto-Acuña and colleagues (2024). Using a different matrix, Maidment and colleagues (2025) did not recover the clade and instead dispersed its putative members across Ankylosauria and Thyreophora. Whether it is a genuine clade sister to Euankylosauria or a convergent Gondwanan grade remains open; Patagopelta and Minmi are contested members placed elsewhere.

Diagnosis

  1. Slender, gracile limbs relative to other ankylosaurs
  2. Thin dermal sacral shield
  3. Dorsoventrally flattened distal caudal osteoderms (in the Stegouros tail weapon)
  4. Teeth with denticles confluent with enamel ridges and an asymmetric bulged cingulum

Genera placed directly in Parankylosauria

  • Antarctopelta Salgado & Gasparini, 2006 Campanian (83.6–72.2 Ma)Antarctica
  • Kunbarrasaurus Leahey et al., 2015 Albian (113.2–100.5 Ma)Australia
  • Stegouros Soto-Acuña et al., 2021 Campanian–Maastrichtian (83.6–66.0 Ma)Chile

References

  1. Soto-Acuña, S.; Vargas, A. O.; Kaluza, J.; Leppe, M. A.; Botelho, J. F.; Palma-Liberona, J.; Simon-Gutstein, C.; Fernández, R. A.; Ortiz, H.; Milla, V.; Aravena, B.; Manríquez, L. M. E.; Alarcón-Muñoz, J.; Pino, J. P.; Trevisan, C.; Mansilla, H.; Hinojosa, L. F.; Muñoz-Walther, V.; Rubilar-Rogers, D. (2021). Bizarre tail weaponry in a transitional ankylosaur from subantarctic Chile. Nature 600(7888): 259-263. Springer Science and Business Media LLC. doi:10.1038/s41586-021-04147-1

    Described Stegouros and named Parankylosauria for the first ancestor of Stegouros but not Ankylosaurus and all its descendants.

    soto-acuña2021a
  2. Soto-Acuña, S.; Vargas, A. O.; Kaluza, J. (2024). A new look at the first dinosaur discovered in Antarctica: reappraisal of Antarctopelta oliveroi (Ankylosauria: Parankylosauria). Advances in Polar Science 35(1): 78-107. doi:10.12429/j.advps.2023.0036

    Redescribed Antarctopelta and recovered it in Parankylosauria with Kunbarrasaurus, Patagopelta and Stegouros.

    soto-acuña2024a
  3. Maidment, S. C. R.; Ouarhache, D.; Ech-charay, K.; Oussou, A.; Boumir, K.; El Khanchoufi, A.; Park, A.; Meade, L. E.; Woodruff, D. C.; Wills, S.; Smith, M.; Barrett, P. M.; Butler, R. J. (2025). Extreme armour in the world's oldest ankylosaur. Nature 1-6. doi:10.1038/s41586-025-09453-6

    New Spicomellus phylogeny dispersed putative Parankylosauria members across Ankylosauria and Thyreophora

    maidment2025b