Tuesday, April 28, 2015

[Paleontology • 2015] Chilesaurus diegosuarezi • An Enigmatic Plant-eating Theropod from the Late Jurassic period of Chile

Chilesaurus diegosuarezi 
Novas, Salgado, Suárez, Agnolín, Ezcurra, Chimento, de la Cruz, Isasi, Vargas & Rubilar-Rogers, 2015

Figure 1: Skeletal anatomy of Chilesaurus diegosuarezi gen. et sp. nov.

Theropod dinosaurs were the dominant predators in most Mesozoic era terrestrial ecosystems. 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. 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). 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).

Dental fossils show that Chilesaurus diegosuarezi did not have sharp, bladed teeth as its relative T. rex did. Here is a side view of its right jaw and teeth.
 (Photo: Fernando Novas)

Theropoda Marsh, 1881

Tetanurae Gauthier, 1986

Chilesaurus diegosuarezi gen. et sp. nov.

Etymology. In reference to Chile, and honoring Diego Suárez, who at the age of 7, discovered the first bone remains in the Toqui Formation.

Locality and horizon. Central Patagonian Cordillera, Aysén (Chile; approximately 46° S); Toqui Formation, Tithonian, latest Jurassic.

Chilesaurus diegosuarezihas characteristics of three different dinosaur groups. Its pubic bone points backward like that of an ornithischian dinosaur, perhaps because it provided the gut more surface area with which to digest plant matter, the researchers said. In most carnivorous dinosaurs, the pubic bone points downward or slightly forward, Carr said.
(Image: Gabriel Lío)

Excavating a Chilesaurus skeleton in beds of the Toqui Formation, Southern Andes, Chile.
At first glance, C. diegosuarezi looks like a perplexing mix of different dinosaurs. But "I think what we're really seeing are the expression of limited options that dinosaurs have when they're herbivores," Carr said. "When you take a meat-eating body and you evolve it into an herbivore, there's only so many options that are available."
(photo: Fernando Novas)

Fernando E. Novas, Leonardo Salgado, Manuel Suárez, Federico L. Agnolín, Martín D. Ezcurra, Nicolás R. Chimento, Rita de la Cruz, Marcelo P. Isasi, Alexander O. Vargas and David Rubilar-Rogers. 2015. An Enigmatic Plant-eating Theropod from the Late Jurassic period of Chile. Nature. (2015) DOI: 10.1038/nature14307

 Chilesaurus, a new raptor-like dinosaur with a vegetarian diet. http://po.st/662q2D @SmithsonianMag  

'Bizarre' Jurassic dinosaur discovered in remarkable new find http://gu.com/p/47q7h/stw
7-Year-Old Boy Discovers dinosaur  https://shar.es/1pd7Bn  @LiveScience