You won’t find a dinosaur defending itself from predators with a completely unique weapon.
in a published study Wednesday in Nature, Chilean researchers have announced the discovery of a new species of ankylosaur, a family of dinosaurs from subantarctic Chile known for their heavy armor. The animal they call Stegouros elengassen offers new clues as to where these tank-like dinosaurs came from, and has a strange, bony tail in the shape of a stick used by Aztec warriors.
“It lacks many of the features we’d expect from an ankylosaur and has a completely different tail weapon, which suggests something very special was going on in South America,” said University of Chile professor and co-author Alexander Vargas. on work.
The northern supercontinent of Laurasia, which once included North America and Asia, once contained a large collection of ankylosaurs. Even in a group of animals famous for their creative approach to defense, the ankylosaur family stands out. Separated from their closest relatives, stegosaurs, in the mid-Jurassic, ankylosaurs developed skins covered with bone deposits called osteoderm, which formed cages of tooth-crushing armor. The most famous ankylosaur species evolved glowing tail clubs like the maces of ancient warriors.
But relatives from Gondwana on the southern continent — now South America and Antarctica — have been less studied, Dr. Vargas. The origins and early evolution of the family have been an enduring mystery, as these are believed to contain the earliest members of the group.
In February 2018, a team of paleontologists from the University of Texas stumbled upon a set of bones in the cold, wind-filled valley of the Río Las Chinas at the southernmost tip of Chile. Despite its gruesome nature, the area is a beacon to paleontologists: Dr. Vargas has spent the last decade there working with researchers, including Marcelo Leppe of the Chilean Antarctic Institute, dating rocks and searching for fossil hotspots.
Texas paleontologist Dr. Vargas and Dr. The field season was only five days away when they alerted Leppe of the finding. Working in very cold conditions at night, they transported the fossil block downhill to the campsite. One person sprained his ankle and another broke a rib. Many people have approached hypothermia.
But getting off the block was worth it. Preparation revealed an unusually complete ankylosaur: 80 percent of a skeleton, including a largely articulated hind half, as well as vertebrae, shoulders, forelimbs, and skull fragments.
When alive, Stegouros would have been about six feet long, with a proportionally large head, slender limbs, and an oddly short tail tipped with seven pairs of flat, bony osteoderms forming a single structure.
That tail gun — Dr. Vargas’s macuahuitlThe obsidian-studded-blade club of Mesoamerican warriors—seems to have evolved independently from other ankylosaurs. Early ankylosaurs from the north did not have tail clubs and later developed them through the evolution of hardened vertebrae, forming the “handle” of the blunt tail club.
The tail club of Stegouros, however, hardens through the fused osteoderms on the vertebrae, forming the distinctive wedge shape. Utah Geological Survey state paleontologist James Kirkland, who was not involved in the study, said the fused osteoderms may have been covered with sheaths of sharp keratin, the material that covers the horns and claws. A blow from the tail would be like “hit the legs with a battle ax,” he said.
Victoria Arbour, curator of paleontology at the Royal British Columbia Museum of Canada, said: the tail looked like of these giant extinct armadillos called glyptodonts. “This is another interesting example of the evolution of bony tails, which seems to have evolved only a few times so far but more than once in ankylosaurs,” he said.
Dr. Overwhelming the anatomical data, Vargas and colleagues concluded that Stegouros was closely related to southern ankylosaurs found in Antarctica and Australia.
After the final separation of Laurasia and Gondwana in the late Jurassic, Dr. Vargas suggested that the two northern and southern ankylosaurs followed different evolutionary trajectories, suggesting the possibility that an entire line of strange ankylosaurs in Gondwana await discovery.
Dr. Kirkland agrees that Stegouros is closely related to Antarctopelta in Antarctica, and even suggests it may be the same animal. But it’s possible that Gondwana was home to multiple ankylosaur lineages, including some more closely related to northern animals. Dr. “It’s not uncommon for a new dinosaur ‘family’ to be discovered,” Kirkland said. “Records for armored dinosaurs in the Southern Hemisphere were pretty weak, and this beast provides clues as to what we’re missing.”
Dr. The Stegouros also represented a breakthrough for Chilean paleontology, Vargas said. Paleontologists argue and debate how to make their domains less dependent on North American and European institutions. The paper, published in Nature, a leading journal led by Chilean paleontologists, was funded by Chilean grants rather than external institutions.
Dr. “This is a very rare case for Chilean science,” Vargas said. “And this is just the beginning. Chile’s fossil record is extremely important to academic success.”