ALT Newly discovered Bagualia alba (illustrated) is one of the oldest true sauropod fossils ever discovered, dating to 179 million years ago. Like other sauropods, B. alba had powerful jaws and an oversized gut, which helped it consume particularly tough plant material.

ALT The classic dinosaur family tree has two subdivisions of early dinosaurs at its base: the Ornithischians, or bird-hipped dinosaurs, and the Saurischians, or lizard-hipped dinosaurs. In this photo-illustration, a drawing of a bird-hipped Ornithiscian is surrounded by fossils of a Pisanosaurus, a small bipedal dinosaur whose fossils have been analyzed in a new study.

ALT The field crew of researchers from Argentina, Brazil, and United States, in the town of Villa Unión, La Rioja Province, Argentina