Where did plant-eaters live?

By the Cretaceous Period, the supercontinent Pangaea had broken apart into separate landmasses that began to look something like the continents we know today. North America was split into two by a great inland sea, Europe was a chain of islands, and India was an island heading north toward Asia. As continents drifted, dinosaur groups became isolated and evolved in different directions - which is why Late Cretaceous Asia and North America have different horned dinosaurs, different duck-bills, and different tyrannosaurs. The horned dinosaurs evolved in Asia and then crossed over to North America via a land bridge across what is now the Bering Strait.

Probably yes. Bone chemistry studies of Pachyrhinosaurus, a horned dinosaur whose remains have been found in northern Alaska, suggest these animals may have migrated seasonally - possibly travelling hundreds of kilometres south each autumn to escape the long, dark Arctic winter, then returning each spring when the lush polar forests came back to life. Other studies of duck-billed dinosaur teeth from western North America suggest they may also have moved between summer and winter feeding grounds, much like caribou today. Not all polar dinosaurs migrated, though - some appear to have toughed out the winters by hibernating or staying active in the cold.

Yes - many sauropods appear to have lived in herds. Fossil trackways in Texas and Australia preserve dozens of sauropod footprints walking in the same direction at the same pace, with smaller (younger) animals in the centre and larger (adult) animals around the outside - a defensive arrangement still used by modern elephants. Mass burial sites containing dozens of individuals of the same species have been found in many parts of the world, suggesting that sauropods like Barosaurus were social animals. Living together gave babies protection from predators and may have allowed adults to share information about food and water.

Many duck-billed hadrosaurs such as Corythosaurus have been found in rocks laid down in coastal floodplains, river deltas, and swampy lowlands. For decades scientists assumed hadrosaurs were aquatic, like hippos - and old illustrations even gave them webbed hands. Modern research has overturned that idea: hadrosaurs were land-dwellers that simply happened to live near water-rich environments where their bodies were more likely to be buried quickly and preserved. They were nimble on land, and probably only entered shallow water to drink or escape predators.

No known plant-eating dinosaur lived in trees. When Hypsilophodon was first described in the mid-19th century, palaeontologists thought it might have perched on branches, using its tail for balance and its sharp toes to grip - similar to a tree kangaroo. That theory has long been abandoned: Hypsilophodon's feet were clearly built for running on the ground, not climbing. Some small meat-eating dinosaurs, like the four-winged Microraptor, probably could climb trees and glide between branches - but among plant-eaters, all known dinosaurs lived on the ground.

• Sauropods generally preferred forest habitats, where dense tree cover provided shade and shelter for their enormous bodies.
• Leaellynasaura, a small plant-eater from Australia, lived inside the Antarctic Circle, where months of total winter darkness alternated with summer daylight - it likely had to be warm-blooded to survive.
• Some of the first dinosaur fossils ever studied were teeth of the plant-eater Iguanodon, discovered in 1822 by Mary Ann Mantell, the wife of an English country doctor.
• All ornithischian (bird-hipped) dinosaurs were plant-eaters.
• By the Late Cretaceous, sauropods had largely disappeared from North America - but they were still thriving in South America, Africa, and India.