Unaysaurus (/"Oo-nay-sore-us"/; "Black water lizard") is a genus of sauropodomorph dinosaur, one of the earliest ancestors of the giant sauropods we know and love. It lived during the Late Triassic period (Norian age), approximately 225-208 million years ago, in what is now southern Brazil.

Description and Classification

Unaysaurus belongs to the Sauropodomorpha, the group of long-necked dinosaurs that includes the iconic sauropods like Brachiosaurus and Diplodocus. However, Unaysaurus was relatively small and walked primarily on two legs.

  • Size: It's estimated to have been about 2.5 meters (8 feet) long and weighed around 70 kilograms (150 lbs).
  • Bipedal: While its later descendants would become massive quadrupeds,Unaysaurus primarily walked on its hind legs.

Distinguishing Features

Unaysaurus possessed a combination of features that set it apart from other early sauropodomorphs:

  • Skull Shape: Its skull had a distinct, boxy shape with unique proportions of certain skull bones.
  • Teeth: The teeth were finely serrated, indicating a herbivorous diet.

Paleoenvironment and Diet

During the Late Triassic, the region where Unaysaurus fossils were found was part of the supercontinent Pangaea. The environment was likely semi-arid. As a herbivore, Unaysaurus would have browsed on the ferns, horsetails, and conifers that made up the vegetation of the time.

Significance and Ongoing Research

Here's why Unaysaurus holds an important place in dinosaur paleontology:

  • Early Sauropodomorph: Represents one of the earliest known and more complete examples of the Sauropodomorpha lineage.
  • Understanding Evolution: Studying it helps paleontologists track how sauropodomorphs evolved from smaller bipedal forms into the towering quadrupedal giants of the Jurassic and Cretaceous.
  • Biogeography: Its close relationship to the German Plateosaurus supports the idea of land bridges that allowed diverse animals to spread across the supercontinent of Pangaea.
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