Guaibasaurus

Phylogeny: Dinosauria > Saurischia > Sauropodomorpha > Guaibasauridae

Overview: Guaibasaurus is counted among the most basal of all known sauropodomorphs, placed within the family Guaibasauridae, for which it’s obviously the namesake. Like most of the earliest, basal sauropodomorphs, Guaibasaurus had a mix of sauropodomorph and theropod-like features. Based on its teeth, we can safely assume it was an omnivore, possibly leaning towards carnivory. It possibly ate a wide range of things including ferns, horsetails, insects, and small vertebrates. Most of its later sauropodomorph relatives were strictly herbivorous, but like all dinosaur lineages, they evolved from a fully carnivorous ancestor. Said ancestor was also a biped, unlike the sauropods or many other more derived sauropodomorphs, but Guaibasaurus itself retained this trait. Overall, it was a lightly built creature with a semi-elongated neck and a long, narrow-snouted skull.

Some potential relatives of Guaibasaurus may’ve included Unaysaurus and Macrocollum, though in recent studies, both are classified in the separate unaysaurid family. Saturnalia is another dinosaur sometimes seen as related to Guaibasaurus, but it’s often classified in a separate Saturnaliidae. In a few studies, Guaibasaurus is classified as more derived than Saturnalia or the related Eoraptor. The first fossils of Guaibasaurus were discovered in the 1990’s, in what is now southern Brazil. Officially described in 1999, its generic name refers to the Rio Guaíba, a body of water present in the region where it was found, a kind of lake or estuary leading from various rivers into a large lagoon. Known fossils of Guaibasaurus come from Brazil’s Caturrita Formation, dating it to around two hundred and twenty-five million years ago, in the Late Triassic.