An enigmatic plant-eating theropod from the Late Jurassic period of Chile

A new dinosaur from the Late Jurassic period of Chile (about 150 million years ago) has been discovered and identified as a primitive kind of theropod that, unusually, was herbivore. An early plant-eating theropod A newly discovered dinosaur species from the Aysén fossil locality in southern Chile has been characterized as a primitive theropod from the Late Jurassic (about 150 million years ago). Theropods, a group that includes Tyrannosaurus and Velociraptor , were generally bipedal and apart from some later highly derived forms, were almost always carnivores. The new species is a relatively early offshoot in theropod evolution but was a herbivore, combining an unprecedented combination of characters and a bizarre anatomy not recorded before among dinosaurs. The discovery illustrates how little we still know about even the broad strokes of dinosaur evolution. Theropod dinosaurs were the dominant predators in most Mesozoic era terrestrial ecosystems 1 . Early theropod evolution is currently interpreted as the diversification of various carnivorous and cursorial taxa, whereas the acquisition of herbivorism, together with the secondary loss of cursorial adaptations, occurred much later among advanced coelurosaurian theropods 1 , 2 . A new, bizarre herbivorous basal tetanuran from the Upper Jurassic of Chile challenges this conception. The new dinosaur was discovered at Aysén, a fossil locality in the Upper Jurassic Toqui Formation of southern Chile (General Carrera Lake) 3 , 4 . The site yielded abundant and exquisitely preserved three-dimensional skeletons of small archosaurs. Several articulated individuals of Chilesaurus at different ontogenetic stages have been collected, as well as less abundant basal crocodyliforms, and fragmentary remains of sauropod dinosaurs (diplodocids and titanosaurians).