Researchers have found the near-complete skeleton of a new species of dinosaur with a unique weapon resembling an Aztec ‘macuahuitl’ war club on its tail.
The find was made in the Rio de las Chinas valley in Chilean Patagonia in February 2018.
The discovery was made during a practical course on fossil extraction and conservation given by palaeontology technician Jonatan Kaluza of the Fundacion de Historia Natural Felix de Azara (Felix de Azara Natural History Foundation) to a group of palaeontologists.
The new species, named Stegouros elengassen, was presented yesterday (Wednesday, 1st December) in the science journal ‘Nature’.
Research on the approximately two-metre skeleton, which was 85 percent complete, shows the species lived some 74 million years ago, during the Late Cretaceous.
The palaeontologists thought at first that the skeleton belonged to an ornithopod, due to its slender limb bones. However, it was only after analysing it in the laboratory did they realise it was actually an ankylosaur.
The Ankylosauria suborder includes the bulk of dinosaurs with armour in the form of bony osteoderms, much like turtles.
The find was particularly unique, as abundant ankylosaur fossils have been discovered in the northern hemisphere, but only fragmentary records had previously been found south of the equator.
The skeleton of a species named ‘A. oliveroi’ in the Antarctopelta genus discovered on James Ross Island in 1986, for example, was only 15 percent preserved.
As reported in a press statement by the Consejo Nacional de Investigaciones Cientificas y Tecnicas (National Scientific and Technical Research Council), an Argentinian government agency, Kaluza said: “[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.”
Stegouros elengassen’s most striking feature is the weapon on its tail, which does not resemble that of any 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 fern frond.” 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.
According to the Nature article abstract, Stegouros elengassen “is related to Kunbarrasaurus from Australia and Antarctopelta from Antarctica, forming a clade of Gondwanan ankylosaurs that split earliest from all other ankylosaurs”.
The find has now challenged the previously-held belief that such weapons had evolved only in species with robust limbs and wide legs.