Stegouros
"roofed tail"
- Lived
- 84 to 66 million years ago, Late Cretaceous
- Diet
- Herbivore
- Group
- Ankylosaurs
- Found in
- Chile
- Named by
- Soto-Acuña et al. 2021
Where its fossils were found
The evidence
Today
75 million years ago
Habitat
It lived on river floodplains in what is now southern Chile. The Dorotea Formation also contains Gonkoken, a duck-billed plant eater.
Field notes
About Stegouros
What it was like
Stegouros was a small armored plant eater with one of the strangest tails of any dinosaur. Instead of a round club or a pair of spikes, the end of its tail was flattened into a broad, frond-shaped weapon made of fused bony plates, edged like a war club.
Its skeleton is nearly complete, which is rare for an armored dinosaur from the southern continents. It belongs to Parankylosauria, a group of small ankylosaurs from the old southern landmass of Gondwana, alongside Antarctopelta from Antarctica and Kunbarrasaurus from Australia.
Its world
It lived in the Late Cretaceous, sometime between about 84 and 66 million years ago, in what is now southern Chile. Its bones come from the Dorotea Formation, which has also produced the duck-billed plant eater Gonkoken.
How it was found
Soto-Acuña and colleagues named Stegouros in 2021, from a single partial skeleton. Its odd tail helped show that the armored dinosaurs of the far south followed their own path, separate from the club-tailed ankylosaurs of the north.
Field gallery
More views of Stegouros
Scenes reconstructed from the available fossil evidence.
1 of 3
Lived alongside
Found in the same rock formations
A rock formation can hold fossils laid down millions of years apart, so not every animal here met Stegouros.
The evidence
The science behind Stegouros
Which parts of the picture come from its own bones, and which come from its relatives.
From its own fossils
- A nearly complete skeleton preserves the skull, slender limbs and much of the body armor.
- Broad bony plates project sideways from the outer half of the tail, forming a flat weapon shaped like a fern frond.
- A separate sheet of bony armor covers the hip region.
Borrowed from relatives
- Most of its body shape comes from its own skeleton rather than from relatives.
- Antarctopelta and Kunbarrasaurus help explain its place among the armored dinosaurs of the southern continents.
Still unknown
- How it swung its tail weapon during an encounter with a predator.
- Its color and the thickness of the coverings over its armor.
- How its tail weapon changed as it grew.
Discovery timeline
- 2015Close relativeLeahey et al.
- 2021Named itSoto-Acuña et al.
- 2023Same rocksAlarcón-Muñoz et al.
Key papers
The research behind what we know of Stegouros
Close relative
Described the skull of Kunbarrasaurus, a southern armored dinosaur later identified as a relative of Stegouros.
Cranial osteology of the ankylosaurian dinosaur formerly known as Minmi sp. (Ornithischia: Thyreophora) from the Lower Cretaceous Allaru Mudstone of Richmond, Queensland, Australia. PeerJ 3: e1475
Read the paper : Cranial osteology of the ankylosaurian dinosaur formerly known as Minmi sp. (Ornithischia: Thyreophora) from the Lower Cretaceous Allaru Mudstone of Richmond, Queensland, Australia (opens in a new tab)Named it
Described the nearly complete skeleton and its flat tail weapon, linking Stegouros with Antarctopelta and Kunbarrasaurus.
Bizarre tail weaponry in a transitional ankylosaur from subantarctic Chile. Nature 600: 259-263
Read the paper : Bizarre tail weaponry in a transitional ankylosaur from subantarctic Chile (opens in a new tab)Same rocks
Named Gonkoken from the same formation, revealing a southern survivor of an early branch of duck-billed dinosaurs.
Relict duck-billed dinosaurs survived into the last age of the dinosaurs in subantarctic Chile. Science Advances 9
Read the paper : Relict duck-billed dinosaurs survived into the last age of the dinosaurs in subantarctic Chile (opens in a new tab)
Close relatives
Other members of Parankylosauria
Sources: Wikidata