Dinosaurs / Triassic / Guaibasaurus
Guaibasaurus
Triassic gwy-bah-SAWR-us, “Guaíba lizard”
Guaibasaurus is an enigmatic early dinosaur discovered in the Late Triassic rocks of Rio Grande do Sul, southern Brazil. Measuring about two metres in length and weighing around ten kilograms, this light-footed biped sits right at the base of the Saurischia, variously classified as a basal theropod or a very primitive sauropodomorph. Its hand possessed five fingers with three large, grasping digits, an ancestral configuration for early dinosaurs. Remarkably, one fossil individual was preserved curled in a resting pose with its hindlimbs folded underneath its torso, showing that this posture evolved near the base of the dinosaur tree. Guaibasaurus was likely an opportunistic omnivore, chasing small vertebrates and insects while browsing on low vegetation in a seasonal, semi-arid environment.
One specimen was found preserved in a resting posture with its limbs tucked beneath the body, much like modern birds.
Where and when
Guaibasaurus lived in the Late Triassic, from 228 to 225 million years ago (Carnian age). Its remains come from Brazil, in the Candelária Formation.
The numbers
Length 1.9 m (estimates run from 1.8 to 2 m). Mass about 11 kg. Hip height about 0.6 m. That is 1.1 human-lengths, or 0.17 of a double-decker bus. These are estimates from partial skeleton; fields marked estimated by the site are length, mass, hip height.