Zupaysaurus (ZOO-pay-SAWR-us, "devil lizard" from the Quechua word "zupay" meaning devil) is an extinct genus of theropod dinosaur from the Late Triassic period, living approximately 228 to 208.5 million years ago. Its fossils were discovered in the Los Colorados Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina by paleontologists A. B. Arcucci and A. C. Rodolfo in 2003. The genus name "Zupaysaurus" was chosen due to the presence of a pair of crests on the skull, which the researchers likened to horns, reminiscent of the devil figure in Quechua mythology.

Description and Classification:

Zupaysaurus was a medium-sized theropod, with an estimated body length of 4 meters (13 feet) based on the size of the recovered skull, which measured approximately 45 centimeters (18 inches) in length. Estimates of its weight vary, with some suggesting 250 kilograms (550 pounds) and others placing it closer to 70 kilograms (154 pounds). Like all theropods, it was bipedal, walking upright on its hind legs and using its shorter forelimbs for grasping prey. The recovered neck vertebrae suggest a relatively long neck for a theropod of its size.

The initial classification of Zupaysaurus placed it among the tetanuran theropods, a group that includes the iconic Tyrannosaurus Rex and Velociraptor. However, further studies have positioned it more basally within the theropod lineage, closer to the coelophysoids, a group of early theropods known for their slender build and long, grasping fingers. Some paleontologists even suggest a closer relationship with Dilophosaurus, another early theropod known for its cranial crests.

Distinguishing Features:

One of the most notable features of Zupaysaurus is the presence of a pair of low, rounded crests running along the top of its skull. These crests, though not as prominent as those seen in Dilophosaurus, are believed to have played a role in display or social interaction. Additionally, Zupaysaurus possessed relatively long and slender limbs compared to other theropods of its size, suggesting adaptations for cursorial locomotion and swift movement.

Paleoenvironment and Diet:

The Los Colorados Formation, where Zupaysaurus fossils were found, represents a diverse ecosystem during the Late Triassic period. Zupaysaurus likely shared its habitat with various other dinosaurs, including early sauropodomorphs like Riojasaurus and Coloradisaurus, making it part of one of the earliest known dinosaur-dominated ecosystems. As a theropod, Zupaysaurus was most likely a carnivore, preying on smaller reptiles, amphibians, and early mammals that inhabited its environment.

Significance and Ongoing Research:

The discovery of Zupaysaurus provides valuable insights into the early evolution of theropod dinosaurs. Its position within the theropod lineage helps paleontologists understand the diversification and anatomical changes that occurred in this group during the Triassic period. Additionally, the presence of features like cranial crests suggests the development of display structures even in these early theropods, potentially indicating complex social behaviors.

Despite the discovery of several partial skeletons, a complete picture of Zupaysaurus anatomy is still lacking. Further research on existing fossil material and the potential discovery of new specimens are crucial for a more comprehensive understanding of this intriguing dinosaur and its place in the evolutionary history of theropods.

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