Gabriel Lio / University of Birmingham via Discovery.com

From the club-tailed Ankylosaurus to the long-necked Brachiosaurus, dinosaurs came in countless shapes and sizes. An especially diverse suborder is called the “theropoda.” The phrase “meat-eating dinosaur” usually refers to some sort of theropod, such as T. rex or Velociraptor. And yet, not all of these guys were built to dine on flesh. The ostrich-like ornithomimids, for example, seem to have had herbivorous dietary preferences, as evidenced by some tantalizing stomach contents discovered millions of years later. Therizinosaurs were also predominantly plant-eaters (as well as scythe-clawed weirdos).

Today, an exciting paper published in Nature has unveiled a strange new theropod, whose carnivorous ancestors decided, at some point, to go vegetarian.

According to Argentinian paleontologist Fernando Novas, the Chilesaurus diegosuarezi's small, leaf-shaped chompers reveal that the bipedal beast was “a strict plant-eater.” One hundred and forty five million years ago, Chilesaurus roamed present-day Patagonia—hence, the name's Chile prefix—a region that has become world-famous as a treasure trove for dinosaur fossils. (The "Diego" included in the second part of the dinosaur's tag is for a 7-year-old named Diego Suarez, who, in 2004, discovered fossilized bones belonging to the creature while visiting the Andes with his parents, geologists Manuel Suarez and Rita de la Cruz.)

By herbivorous theropod standards, Chilesaurus is fairly unusual, as the varieties mentioned above emerged tens of millions of years after this little critter evolved. When it first showed up, only a few other theropods had made the switch to a plant-eating lifestyle (among them: China’s birdlike Limusaurus). 

In addition to its distinctive dental anatomy, Chilesaurus’ features included a beak, a small, rounded skull, and modest forelimbs topped with two clawed fingers apiece.