Stegouros elengassen is a recent discovery in the world of dinosaurs. This armored dinosaur, unearthed in southern Chile, has captured scientific attention due to its unusual tail. Its unique features challenge previous understandings of armored dinosaur evolution, reshaping how researchers classify and interpret the diversity of its group.
Discovery and Initial Description
Stegouros elengassen was unearthed in 2018 in the Dorotea Formation, situated near Puerto Natales in the Magallanes region of southern Chile. A team from the Chilean Antarctic Institute (INACH), led by Alexander Vargas from the University of Chile, conducted the excavation. The discovery was notable for the exceptional preservation of the skeleton, providing scientists with a nearly complete specimen.
This dinosaur measured approximately 2 meters (about 6.5 feet) in length and weighed between 150 and 250 kilograms (around 330 to 550 pounds). This size places Stegouros in the range of a small armored dinosaur. Its body was covered in osteoderms, bony plates embedded in the skin, providing a protective armor layer.
The Remarkable Tail Weapon
The unique tail weapon is the most distinctive feature of Stegouros elengassen. Unlike the heavy, rounded tail clubs of typical ankylosaurs, Stegouros possessed a flattened, frond-like structure. This weapon was composed of seven pairs of laterally projecting osteoderms, fused to form a blade-like structure encasing the distal half of its tail.
This unusual tail has been compared to a macuahuitl, an ancient Aztec wooden club with obsidian blades along its sides, due to its flat, slashing appearance. Scientists hypothesize that Stegouros would have swung this tail from side to side for defense against predators. The tail’s design suggests a different evolutionary path for tail weaponry compared to the more familiar tail clubs or spikes seen in other armored dinosaurs.
Evolutionary Insights and Classification
The discovery of Stegouros elengassen has provided insights into the evolutionary history of armored dinosaurs. It is classified as an ankylosaurian, but its primitive postcranial skeleton, featuring some stegosaur-like characteristics, challenges previous understandings of this group.
Stegouros belongs to a newly recognized group called Parankylosauria, a clade of small armored dinosaurs from Gondwana, the ancient southern supercontinent. This lineage diverged very early from other ankylosaurs, such as the Ankylosauridae and Nodosauridae families, which are typically found in the Northern Hemisphere. The existence of Stegouros and its relatives, like Kunbarrasaurus from Australia and Antarctopelta from Antarctica, suggests a distinct evolutionary path for armored dinosaurs in the Southern Hemisphere.
Ancient Habitat and Lifestyle
Stegouros elengassen lived during the Late Cretaceous period, approximately 71.7 to 74.9 million years ago. Its fossil was found in the Dorotea Formation in the Magallanes region of southern Chile, a location that bordered Antarctica during that geological time.
Scientists infer that Stegouros was a herbivore, as indicated by its small skull, broad snout, and teeth designed for cutting low-lying vegetation. Its armored body and unique tail weapon suggest that it used these features for defense against predators that shared its habitat. Fossils of amphibians, mammals, fish, reptiles, and other dinosaurs have also been discovered in the Dorotea Formation, painting a picture of a diverse ancient ecosystem.