Guaibasaurus was originally named on the basis of the holotype, MCN PV2355, a well-preserved partial postcranial skeleton and the paratype, MCN PV2356, an articulated and nearly complete left hindlimb, which were discovered in the "Sesmaria do Pinhal 2" locality near Candelária, Rio Grande do Sul, in Brazil, in the geopark of Paleorrota.
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The specific name is named after Candelária, a city near the fossil locality in which the holotype was found.
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The referred materials were collected from the "Linha São Luiz" locality near the town of Faxinal do Soturno, Rio Grande do Sul, also in the geopark of Paleorrota.