Құрып кеткен Гуаибазавр динозавры

Extinct genus of dinosaurs

Guaibasaurus is an extinct genus of basal saurischian dinosaur known from the Late Triassic Caturrita Formation of Rio Grande do Sul, southern Brazil. although there are some suggestions that it was a theropod instead. In 2016 Gregory S. Paul estimated it at 2 meters (6.6 ft) and 10 kg (22 lbs), whereas in 2020 Molina Pérez and Larramendi listed it at 3 meters (10 ft) and 35 kg (77 lbs).

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 upper portion of the Candelária Sequence or the Caturrita Formation. Specimen UFRGS PV0725T is articulated with hindlimbs tucked underneath its body and forelimbs flexed to the side. Although most of the neck is not preserved, the vertebrae at the base of the neck are present in UFRGS PV0725T and curve to the left, suggesting the entire neck was curved toward the left side of the body. The posture of this skeleton is similar to the resting position of birds, and is otherwise primarily known from advanced maniraptoran dinosaurs that are closely related to birds. It has also been observed in the dinosauriform Saltopus. Like living birds, Guaibasaurus may have rested in this position to conserve body heat. Guaibasaurus was first named by José F. Bonaparte, Jorge Ferigolo and Ana Maria Ribeiro in 1999 and the type species is Guaibasaurus candelariensis. The generic name is named after the Rio Guaíba hydrographic basin where the holotype was found as a part of the "Prό Guaíba Project", a scientific program supporting research on fossils from the Triassic period. The specific name is named after Candelária, a city near the fossil locality in which the holotype was found.

José Bonaparte and colleagues, in their 1999 description of the genus, found it to be possible basal theropod and placed it in its own family, Guaibasauridae. Bonaparte and colleagues (2007) found another early Brazilian dinosaur Saturnalia to be very similar to it, and placed the two in the Guaibasauridae which was found to be a primitive saurischian group. Bonaparte found that these forms may have been "prosauropods" (primitive sauropodomorphs), or an assemblage of forms close to the common ancestor of the sauropodomorphs and theropods. Overall, Bonaparte considered that both Saturnalia and Guaibasaurus were more theropod like than "prosauropod" like. while others consider it a basal sauropodomorph. Other members of "Guaibasauridae" (such as Saturnalia) are generally considered to be very basal sauropodomorphs, and may or may not form a clade with Guaibasaurus. An article depicting a novel phylogenetic hypothesis for silesaurids also recovers Guaibasaurus as a sauropodomorph, but close related to the coeval Unaysaurus and Macrocollum, rather than early forms such as Saturnalia.