A new species of ankylosaurus protected itself from predators with a tailed weapon unlike anything else in the fossil record. In fact, in an attempt to describe it, the best comparison a dinosaur descriptor can find is the Mesoamerican war club, macuahuitl.
The advantages and disadvantages of these severed blades over the spikes and ligaments developed by other armored dinosaurs remain a mystery, but the discovery suggests that the Cretaceous species of Gondwana needed the same protection as their northern hemisphere counterparts.
In the face of the fearsome predators of the time, many herbivorous dinosaurs lacked armor, which resulted in the development of a tail that could cause extensive damage to the legs, and possibly the soft stomach, of anything that tried to eat it. Some may also find this useful in mating struggles with their own species.
Paleontologists failed to develop a more scientific term, and adopted the name “Tagomaiser” in honor of Gary Larson’s cartoon. An article in Nature describes a recently identified Cretaceous Chilean ankylosaurus with its defining characteristics, one that even the title of the article considers to be an “alien.”
The find was different enough from anything known to require a new genus, and the authors named it Stegouros, which is confusingly unrelated to the famous Stegosaurus. The name comes from the Greek words meaning “roof” and “tail”; Stegouros lived 80 million years later and on the other side of the world with almost the same name. The species name is elengassen.
Only one Stegouros fossil has been found, which is a stark contrast to the common Stegosaurus, but this one is nearly complete. With a length of 180-200 cm (6-7 ft), including the tail, it is believed to be an adult.
The tail is relatively short by armored dinosaur standards and ends with seven pairs of flat bony sediments that form a shape somewhat resembling a fern leaf, for those unfamiliar with ancient Aztec weapons. You tend to investigate any potential threats.
Elengassen had a skull and teeth similar to those of other types of ankylosaurs, including the most common representatives of the Northern Hemisphere. However, the rest of its body looks like it was from the past, including some features that actually resemble that of a stegosaurus.
Elengassen was found in layers dating from 74.9-71.7 million years ago from Magellan as the southern tip of Chile. The site was a delta at a time when many dinosaurs and other animals were trapped. At that time, South America was still connected to Antarctica and Australia as part of the supercontinent Gondwana. Its closest known relatives appear to be the greater Antarctica and the Australian Conparasaurus, but Stegurus has some important differences between the two. The authors proposed a new clade called Parankylosauria (“next to the ankylosaurs”) to incorporate them. Parankylosaurs lacked many of the characteristics of the “true” ankylosaurs that existed in the mid Jurassic period, about 165 million years ago. Therefore, the roots of Parankylosaur must be very ancient, before that date,” said Dr. Alexander Vargas of De Chile university in a statement.
The authors still believe that ankylosaurs were actually less common in the southern hemisphere than in the northern, but our limited knowledge of Gondwana’s species also partially reflects the amount of exploration that has taken place there. No dinosaurs had been described from Chile before 2011, and Stegouros is the fourth in ten years.
While they may not be common, the fact that the Southern Hemisphere’s line of ankylosaurs is nearly 100 million years old suggests that the animal kingdom reservoir might still exist today, were it not for an intervening asteroid.
with information from Ilmu IFL
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