The Gualicho shinyae — nicknamed Gualicho — is a theropod, a two-legged, bird-like dinosaur. It stretched an imposing six meters (nearly 20 feet) from head to toe, and weighed an estimated 450 kilograms (1,000 pounds).
It roughly resembles the Tyrannosaurus rex but Gualicho, found in the north of Argentina’s Patagonia region, was not a close relative of the king of dinosaurs.
Its stubby limbs evolved independently and not from a shared, short-armed ancestor — a clue that may help researchers better understand how the extinct animals evolved.
“This is a completely different lineage. We just froze up when we realized it,” Sebastian Apesteguia, a researcher at Argentina’s National Scientific and Technical Research Council told a briefing in Buenos Aires.
Its only known ancestor is the Deltadromeus, a leggy, carnivorous dinosaur with slender arms found in Niger.
The research on Gualicho in the scientific journal Plos One was led by Apesteguia and Ruben Juarez Valieri, a specialist in carnivorous dinosaurs in Argentina’s Rio Negro province.
The new dinosaur’s name Gualicho is in honor of a local indigenous diety with power over animals and the wind. And Shinyae is in honor of Akiko Shinya, chief fossil preparator at Chicago’s Field Museum, who found the incomplete skeleton while working on the dig.
“We found Gualicho at the very end of the expedition. Pete joked, ‘It’s the last day, you’d better find something good!’ And then I almost immediately was like, ‘Pete, I found something.’ I could tell right away that it was good.”
She was referring to Peter Makovicky, The Field Museum’s curator of dinosaurs.
“Gualicho is kind of a mosaic dinosaur, it has features that you normally see in different kinds of theropods,” Makovicky said in a statement.
“It’s really unusual — it’s different from the other carnivorous dinosaurs found in the same rock formation, and it doesn’t fit neatly into any category.”
“By learning more about how reduced forelimbs evolved, we may be able to figure out why they evolved,” Makovicky added.
Most of the recovered fossils are in the Patagonia National Sciences Museum and a provincial museum in the Argentine city of Cipolletti.