A new dinosaur species named Gualicho shinyae was described in PLOS ONE. It was named after its discoverer Akiko Shinya and “gualicho,” a Spanish name for a Patagonian belief representing bad luck. The specimen was found in the Patagonia region, in the southern flat lands of Argentina, specifically on the Huincul Formation.

The finding occurred the last day of the expedition. The Gualicho features a distinctive characteristic shared by the T. rex, short and skinny arms, paired with massive jaws. The Gualicho’s hands have two long fingers and a little stub corresponding to a third finger. This species, although similar to the T. rex, is from the Allosaurus family, with much larger arms and three fully developed fingers.

This species, although akin to the T. rex, is from the Allosaurus family, with much greater arms and three fully developed fingers. Image Credit: Pop Sci
This species, although akin to the T. rex, is from the Allosaurus family, with much greater arms and three fully developed fingers. Image Credit: Pop Sci

The fact that the Gualicho’s fingers were different highlights a fascinating evolution variation that may be due to the species’ relationship with its biological environment. Scientists are not entirely certain about the reason behind the reduction of theropod’s upper limbs.

The ‘curse’ of tiny T. rex arms

Theropoda is a group of mostly carnivorous dinosaurs, from which birds are thought to have evolved from due to both having a wishbone, air-filled bones, the trait of brooding their eggs, and in some cases, feathers.

Theropods, such as the Gualicho, the T. rex and the Carnotaurus, all share the similar feature of skinny and short arms. Thomas Holtz, Jr. from the University of Maryland believes that it may be due to these dinosaurs using their hands less and less, relying on their jaws and feet to hunt for prey. Also, smaller arms would allow the dinosaur’s neck muscles to develop extensively, allowing for a much stronger jaw.

Finding the T. rex’s Argentinian cousin, Gualicho

The expedition started on 2007. The researchers managed to find several pieces of a theropod’s fossil and coprolites (the scientific term for ‘poop fossil’). One of the archaeological sites was owned by a sheep farmer, who took almost eight years to allow the archaeologists to dig on his land. As the digging took place, a truck that archaeologist Peter Makovicky was driving got overturned. Luckily, there were no significant damages other than the vehicle, which was completely wrecked.

On the last day of the expedition, the Gualicho was found as Makovicky jokingly told Akiko Shinya “to go find something good.” They discovered the Gualicho’s tail, column, scapula, and portions of its forelimb and hind limbs. Years had passed before the local government allowed the fossil to be retrieved. According to lead researcher Sebastián Apesteguía, the digging process saw a presidential election and a new political direction. The Museo Patagónico de Ciencias Naturales unearthed the fossil and prepared its analysis.

The specimen dates from the Late Cretaceous, and its fossil suggested that it was able to stand on its muscular hind legs, allowing it to reach considerable speed. The archaeologists named the 1,000-pound Gualicho as a sister of the Deladromeus, native to Africa. The discovery shows that there are significant archaeological similarities between the Huincil Formation and the Kem Kem deposits in Niger, located in North Africa. The Huincul Formation has already yielded several species of dinosaurs, including the massive Argentinosaurus, the Mapusaurus, the Cathartesaura and the Skorpiovenator genera.

The researchers questioned if the Gualicho's limbs evolved by their own or if it is a complementary trait of its genes. Image Credit: The Guardian
The researchers questioned if the Gualicho’s limbs evolved on their own or if it is a complementary trait of its genus. Image Credit: The Guardian

The Gualicho shares several ceratosaurian, and tetanuran Ceratosaurus was a larger predator, but smaller than a T. rex, with a horn and stunted arms, while tetanurae is a family which includes the vast majority of theropod dinosaurs.

The dimensions of its bones were measured and compared using sophisticated algorithms to other species in order to determine similarities between each known theropod. The Gualicho’s arms were compared to those of a small child. Makovicky highlighted the Gualicho as a “mosaic dinosaur,” as it has many features that are usually found in other theropods. It is unlike any other predator found before and cannot be easily added to an existing category.

Although most theropods have shortened forelimbs, some exceptions to the rule are spinosaurids and coelurosaurs, with some species going as far as using their four limbs for walking, as it is the case of the Xuanhanosaurus genus. The earliest theropods were found in Argentina, but they are also a frequent find in India and Southern Africa. The most popular group of theropods are the coelurosaurs, including the Tyrannosaurus rex, the Velociraptor and the feathered families of oviraptorosaurs and troodontids.

Gualicho is a native word that means ‘to people’. It is a being that personifies every cause of evil and bad omens on the indigenous villages of Patagonia. Gualicho is generally linked to “harm,” and the entity is usually believed to hide in lonely trees, large rocks, caves, and other eerie natural structures. As Spanish conquistadors made it to Patagonia, Gualicho was mistakenly associated with the devil, but the word usage managed to stick to that of “bad omen,” perhaps to highlight the Gualicho’s short and stumpy arm heritage.

The Gualicho’s colorful name comes from all of the obstacles that the archaeologists had to face since the fossil’s discovery. Paleontologists had to deal with the truck flipping over, the landowner’s reluctance to let the researchers in his farm, and the years lost while waiting for the government to approve the fossil’s extraction finally.

Source: Smithsonian