T-rex had huge teeth. Raptors sported sharp, scythe-like claws. Triceratops fought with head-mounted horns. The ancient arsenal of dinosaur warfare was varied, and now a brand new weapon has been added to the collection. Paleontologists have discovered a new type of ankylosaur with a tail like a battle axe.
Ankylosaurs are those armored dinosaurs built like tanks, covered in bony plates and spikes and often brandishing a heavy tail club that no carnivore would want anywhere near its kneecaps. But the new species takes a different tack, attacking with a tail armed with seven pairs of large, flat spikes that its discoverers liken to an Aztec battle axe.
As such, the species has been named Stegouros elengassen – the first part means “roofed tail,” while the second is the name of a mythical armored monster in the folklore of the Aonik'enk people native to the region of Patagonia where it was found.
Stegouros was about 2 m (6.6 ft) long, and if you were standing next to one it probably would have only stood as high as your hip. It lived about 74 million years ago in a river delta environment.
While the axe tail was the most obvious oddity in the almost-complete skeleton, the scientists noticed some other strange features too. Stegouros was clearly an ankylosaur, but it lacked some traits common to later members of the family. At the same time, it showed some unexpected similarities to stegosaurs, a related group of armored dinosaurs known for the large vertical plates along their backs and a spiked tail weapon.
The researchers concluded that Stegouros was a transitional species of ankylosaur, and even went as far as to formally propose a new clade, the Parankylosauria. This group would include other ankylosaurs discovered in Antarctica and Australia – essentially, those that lived on the ancient southern supercontinent Gondwana. Existing species found across the Northern Hemisphere would now fall under the name Euankylosauria.
The team says that further digs may turn up other Parankylosauria species with similar axe-like tails.
The research was published in the journal Nature.
Source: University of Chile