Zupaysaurus, meaning “devil lizard,” is a genus of theropod dinosaur from the Rhaetian stage of the Late Triassic, and possible the Hettangian stage of the Early Jurassic Period of what is now Argentina. It was discovered in the Los Colorados Formation of La Rioja province in Argentina. The formation is normally assigned to the Norian stage (216-203), but has also been assigned to the slightly younger Rhaetian stage (203-200 million years ago), where Zupaysaurus was found.

The type species, Z. rougieri, was named after Guillermo Rougier, the scientists who led the expedition which discovered and collected the specimen. Zupaysaurus was described and named in 2003 by
Argentine paleontologists Andrea Arcucci and Rodolfo Coria. Their work was published in the journal Ameghiniana.

Zupaysaurus was originally classified as the earliest known tetanuran theropod based on several features of its skull and hind limb. However, several features typical of more primitive theropods were also noted by the original authors. More recent analysis seems to be in favor of the later assessment. The new findings would place Zupaysaurus as a coelophysoid.

Only one specimen of Zupaysaurus is known. It includes a nearly complete skull, right shoulder girdle, lower right leg and ankle, and twelve vertebrae from the neck, back and hips. Additional material found at the site may or may not belong to Zupaysaurus. It is housed at the National University of La Rioja in La Rioja, Argentina.

Zupaysaurus is believed to have been a bipedal predator, measuring up to 13 feet long, based on its skull — which measured 18 inches long. It may have had two parallel crests running the length of its snout. Like all known theropods, it walked upright on its hind legs, leaving the forelimbs free to grasp prey. As seen in many early theropods, the bones of the ankle were fused together.

The skull bore two thin parallel crests, similar to other theropods. However, the crests were allegedly formed by the nasal bones solely, unlike those of many other theropods. Crests on the skull were pervasive among theropods and may have been used for communication and/or species or gender recognition.

However, more recent analysis of the skull casts doubt on the presence of these crests in Zupaysaurus. An unpublished study of the skull indicated the structures initially identified as crests were in fact lacrimal bones — tear ducts — displaced upwards during the fossilization process.

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