An enigmatic dinosaur with a slashing tail that has perplexed scientists for years was presented to the public on Wednesday by Chilean paleontologists, three years after its nearly intact remains were discovered in Patagonia, in the southern Chilean province of Santa Cruz.
In February 2018, a group of 19 scientists conducted excavations at Cerro Guido, a dinosaur-remains hotspot located in a rugged area of Chilean Patagonia where they discovered rocks containing bones that appeared to be those of an ornithopod dinosaur. The bones were identified as those of an ornithopod dinosaur.
However, the vestiges of a tail came out of nowhere from the depths of the ground, which perplexed them.
During the presentation of the discovery at the University of Chile, which included the participation of government officials, one of the paleontologists, Alexander Vargas, explained that the tail was covered with seven pairs of dermal bones, five of which were fused in the middle of the tail, producing an “absolutely different weapon” than anything that had previously been known about any dinosaur. “It’s a really unusual weapon. Books on prehistoric animals for kids need to update and put this weird tail in there. … It just looks crazy,” he said.
A second surprise for the specialists was the fact that they were able to uncover 80 percent of the dinosaur skeleton.
Following extensive research, they determined that the species existed in the region between 71 and 74.9 million years ago. Herbivore, it was around two meters in length and weighed about 150 kg.
The finding was also published in the prestigious scientific magazine Nature, which is widely respected.
There were seven pairs of laterally protruding dermal bones on the highly odd tail, giving it an appearance comparable to that of a fern frond or the “Macuahuitl,” a battle club used by the ancient Aztecs who occupied Central America.
This characteristic, in particular, gave birth to the name “Stegouros elengassen,” which was given to the dinosaur by scientists. Stegeouros means “roof tail,” and “elengassen” is the name of a fabled armored monster in the tradition of the ancient Patagonian or Tehuelche peoples who lived in southern Argentina and Chile centuries ago.
It is believed by experts that the remains represent a previously undiscovered lineage of an “armored” dinosaur that has never been seen before in the southern hemisphere, but which exhibits characteristics that are similar to those of other species already known from the northern half of the continent, including paired spiked tails like Stegosaurus and a large, rounded mace on the tail of ankylosaurs that lived in both hemispheres.
“We are unable to determine why a structure such as this (the tail) came into being. For what it is worth, we know that among groups of armored dinosaurs, there seems to be a propensity for them to evolve independently diverse protection systems based on dermal bones,” he said.
Argentinean authorities discovered the fossilized remains of Stegeouros in the Las Chinas valley near Cerro Guido, close to the border with Chile (about 3,000 km south of Santiago). There are various distinct rock formations that contain fossils that have been examined by experts for several years in an area that is about 15 kilometers squared.
These fossils have served as “a type of book” for paleontologists, allowing them to “understand the successions of flora and fauna that occupied that site.” They have also allowed them to uncover the proximity that existed millions of years ago between what is now America and Antarctica.
In addition, “we have two armored dinosaurs closely connected to it (Stegeouros),” Soto said, “there is different strong evidence that there is a biogeographic relationship with other portions of the earth, in this instance Antarctica and Australia.”
“Much of the biota that forms in the southern tip of South America and that we have preserved to this day – for example, the Nothofagus forests (trees and shrubs of the southern hemisphere) – is likely to have originated from the meeting of these continents and the communication that allowed these floras and fauna, such as these dinosaurs, to roam freely,” he continued.