The Guaibasaurus means Guaiba lizard. Fossils were found from Geopark of Paleorrota, Rio Grande do Sul, Brazil. The species was described by Jose Bonaparte and J. Ferigolo, and Ribeiro in the year 1999.

The Guaibasaurus could be a Staurikosaurus and Herrerasaurus classification, but there are many features of the fossils that line up well with Prosauropoda and Theropoda. Today it is absolutely unknown.