Saturnaliidae is considered the most primitive known family of sauropodomorphs, dating to the Carnian stage of the Late Triassic, roughly 233 million years ago, making its members among the very earliest dinosaurs in the fossil record. Saturnaliids were small, bipedal plant-eaters, typically only 1 to 2.5 meters long, with a long neck that would have let them browse foliage higher than most contemporaries, teeth with basally constricted, leaf-shaped (lanceolate) crowns, and dental features suggesting a diet that may have included both plants and small animal prey.
The family takes its name from Saturnalia, described from the Late Triassic of Brazil, and includes Panphagia and Eoraptor -- the latter more often discussed as an early theropod or a dinosaur of uncertain affinity -- both from the Ischigualasto Formation of Argentina, plus the more recently described Mbiresaurus from Zimbabwe. By the time these animals were alive, both major dinosaur lineages, Saurischia and Ornithischia, had already split, and Saturnaliidae's position at the very base of Sauropodomorpha makes it central to understanding what the ancestral dinosaur body plan looked like before the group diversified into theropods, sauropods, and their relatives.