Pronunciation: GWIE-bah-SOR-us
Meaning: Guaíba lizard
Author/s: Bonaparte (1999)
Synonyms: None known
First Discovery: Rio Grande do Sul, Brazil
Discovery Chart Position: #451
Guaibasaurus candelariensis
Guaibasaurus is a dinosaur from the Triassic Santa Maria beds of Brasil's Rio Grande do Sul, which is more enigmatic than Mona Lisa's smile due to a bizarre suite of features that have long puzzled paleontologists.
With flexed forelimbs, hindlimbs tucked under its body, and neck curved to one side, a specimen of Guaibasaurus (UFRGS-PV-0725-T) described in 2007 seems to have died in a roosting position akin to birds. Paleontologists were perplexed because they had latched onto features in earlier finds that are common in herbivorous dinosaurs and convinced themselves that its affinities lay with Sauropodomorpha. But this new specimen added weight to Bonaparte's initial inkling that Guaibasaurus and thus its family (Guaibasauridae) were archaic members of Theropoda; the mostly carnivorous lineage that led to our modern feathered friends.
Since then, most analyses have recovered all but one guaibasaurid as sauropodomorphs, and not necessarily closely related ones, the exception being Guaibasaurus itself, which pretty much renders its family moot. According to latest research Guaibasaurus is almost certainly an archaic theropod, but with some prosauropod features thrown in to cause confusion. Or... perhaps it's a primitive saurischian straddling the junction where Theropoda and Sauropodomorpha went their separate ways, hence the presence of common characteristics.
With flexed forelimbs, hindlimbs tucked under its body, and neck curved to one side, a specimen of Guaibasaurus (UFRGS-PV-0725-T) described in 2007 seems to have died in a roosting position akin to birds. Paleontologists were perplexed because they had latched onto features in earlier finds that are common in herbivorous dinosaurs and convinced themselves that its affinities lay with Sauropodomorpha. But this new specimen added weight to Bonaparte's initial inkling that Guaibasaurus and thus its family (Guaibasauridae) were archaic members of Theropoda; the mostly carnivorous lineage that led to our modern feathered friends.
Since then, most analyses have recovered all but one guaibasaurid as sauropodomorphs, and not necessarily closely related ones, the exception being Guaibasaurus itself, which pretty much renders its family moot. According to latest research Guaibasaurus is almost certainly an archaic theropod, but with some prosauropod features thrown in to cause confusion. Or... perhaps it's a primitive saurischian straddling the junction where Theropoda and Sauropodomorpha went their separate ways, hence the presence of common characteristics.
(Guaíba lizard from near Candelária)Etymology
Guaibasaurus is derived from "Guaíba" (after the "Rio Guaíba Hydrographic Basin" where the holotype was found as a part of the "Pró-Guaíba Project", a scientific program supporting research on fossils from the Triassic period) and the Greek "sauros" (lizard). The species epithet (or specific name), candelariensis (kahn-day-LAHR-ee-EN-sis), is named after Candelária, a city near the fossil locality in which the holotype was found.
Discovery
The remains of Guaibasaurus were discovered in the Caturrita Formation, west of Candelária, Sesmaria do Pinhal 2, Rio Grande do Sul, Brazil.
The holotype (MCN PV2355) is a skulless partial skeleton including vertebrae, parts of ribs, shoulder bones, pubes and ischia (hip bones), a partial hind limb and feet.
