Toothy tyrannosaurs and enormous titanosaurs may be the most dramatic dinosaurs of the Late Cretaceous, but plant-eating hadrosaurs had the numbers. These widely-distributed animals, often called duck-billed dinosaurs, are among the most commonly found fossils from the period that stretched 66 million-100 million years ago. Yet the hadrosaur origin story remains a bit of a mystery. Today, a magnificent new find from Mongolia fills in some of the gaps.

Paleontologists unearthed multiple