Credit: Jorge González and Pablo Lara
Like T. rex, the newly discovered Gualicho shinyae had two clawed fingers at the end of its small arms.

A new dinosaur species has been found during excavations in Argentina. And there is something very special about it.

The new dinosaur has been named Gualicho shinyae and was a theropod dinosaur, walking on two legs. Theropods were ancestrally carnivorous, although a number of theropod groups evolved herbivory, omnivory, piscivory, and insectivory.

It was unearthed in Argentina’s Huincul formation, rich in dinosaur fossils. The Huincul formation is renowned for several remarkable dinosaur fossils, including Dreadnoughtus schrani and Argentinosaurus – perhaps the largest dinosaurs ever.

Just like the famous Tyrannosaurus Rex, this predatory dinosaur had very short arms with only two claws. However, it is not at all closely related to the Tyrannosaurus.

Although the skeleton was incomplete, the authors estimate that the dinosaur was likely a medium-sized slender predator weighing around a half ton, similar in size and weight of a polar bear.

These unusually short arms are much more similar to those of the distantly related (T. rex) than more closely-related species and may thus indicate that the forelimbs evolved independently on two branches of the evolutionary tree, rather than arising from a common short-armed ancestor

The scientists now hope that this fossil can provide clues to why short arms were developed.

The study An unusual new theropod with a didactyl script from the Upper Cretaceous of Patagonia was published July 13, 2016 in the open-access journal PLOS ONE

Reference: Sebastian Apesteguía et al. An unusual new theropod with a didactyl script from the Upper Cretaceous of Patagonia, Argentina. PLOS ONE, 13 July 2016. DOI: 10.1371 / journal.pone.0157793)