A brand new dinosaur with an axe-like tail has been unearthed by scientists.
Archaeologists discovered the near-complete skeleton of the new species, named Stegorous elengassen, in Chilean Patagonia in 2018.
Researchers say its stand-out feature is a unique weaponised tail, which resembles a war club used by the Aztec people of South America.
Just like the "macuahuitl" axe, the dinosaur's tail is flat with jagged edges and it was designed to inflict damage.
The 2018 find - which was featured in the "Nature" science journal yesterday - was even more unique because it was the first of the dinosaur's subspecies found below the equator.
Scientists have found abundant ankylosaur fossils in the northern hemisphere, but only fragments have been unearthed in the global south.
The dinosaur's skeleton was 85 per cent complete at the time of its discovery.
Palaeontologists dated its bones to some 74 million years ago, during the Late Cretaceous period.
The two-metre long beast was found during a university fossil extraction and conservation course being held by a university.
At first, scientists thought the creature was an ornithopod, which has long slender limb bones, just like the find.
But laboratory analysis showed it was an ankylosaur, which are known for their armoured bodies.
The Ankylosauria suborder includes the bulk of dinosaurs with armour in the form of bony osteoderms, much like turtles.
An Argentinian government agency, the National Scientific and Technical Research Council, wrote in a press statement: "[W]e came to the conclusion that it is a transitional ankylosaur, that is, an evolutionary link between ankylosaurs and other older lineages of armoured dinosaurs."
The creature's weaponised axe-like tail has not been seen in any other known dinosaur.
According to the press statement: "It is a large weapon composed of seven pairs of osteoderms (dermal bones) projected laterally in a manner similar to a fernfrond."
It also apparently resembles a macuahuitl, an Aztec weapon of war.
Until the discovery of the new species, there had been no record of a slender-limbed armoured dinosaur that also had a weapon on its tail.
The find has now challenged the previously-held belief that such weapons had evolved only in species with robust limbs and wide legs.
