Stegouros
| Key | Value |
|---|---|
| Name Meaning | “roofed tail” |
| Location | Chile |
| Time Period | c. 72 million years ago (Late Cretaceous) |
| Length | 5 ft (1.5 m) |
| Weight | 220 lb (100 kg) |
| Locomotion | Quadruped |
| Diet | Herbivore |
| Described | 2021 (Soto-Acuña et al.) |
| Geological Formation(s) | Dorotea |
| Valid Species | Stegouros elengassen (type) |
Phylogeny: Dinosauria > Ornithischia > Genasauria > Thyreophora > Thyreophoroidea > Eurypoda > Ankylosauria > Parankylosauria
Overview: Stegouros hasn’t been known to science for very long, but its very discovery has proven quite significant. Bones of the animal were reported in 2018, found in the southern region of Chile (part of the larger Patagonian region in South America). Described in 2021, the generic name of this genus means “roofed tail”, taken from the same root word in the name of the famed Stegosaurus. It was chosen in reference to the bony plates that radiated out from the lower half of its tail. This feature was formed by rows of wide, pointed osteoderms, forming a structure informally referred to as a “macuahuitl”, referencing the obsidian studded war clubs used by the Aztecs and other related cultures. Stegouros probably employed it as weapons as well, to strike out at attackers or for driving away competing members of its own species with side-to-side strikes. The latter behavior has strong evidence among some of its ankylosaurian relatives.
Possessing a new style of tail club wasn’t the only notable aspect about Stegouros. The scientists who studied and described its fossils concluded that it belonged to a previously unknown southern lineage of ankylosaurs called the Parankylosauria, also established by them in 2021. Some notable potential members included Antarctopelta, Kunbarrasaurus, Patagopelta, and possibly Minmi. All of these dinosaurs lived in South America, Antarctica or Australia. They were basal ankylosaurs that branched off from their relatives quite early on in the clade’s evolution. Most, like Stegouros itself, were very small by ankylosaur standards. Stegouros was less than two meters long, having an unusually short tail on top of that. Either way, the parankylosaurs weren’t lacking in armor. Bony scutes still grew over their necks, sides, backs, and upper tails. Stegouros fossils are known from the rocks of the Dorotea Formation, meaning it lived fairly late into the Cretaceous Period, around seventy-two million years ago.