How did plant-eaters find food?

Sauropods were the lawn-mowers of the Mesozoic - they had to eat constantly to fuel their enormous bodies. A big sauropod like Argentinosaurus probably needed several hundred kilograms of plants every day. They likely fed mostly on tough, fibrous conifer needles, ferns, and horsetails. Their long necks allowed them to graze across huge areas without moving their bodies, sweeping their heads from side to side like a giant living crane - and some palaeontologists think their constant feeding may have created "browse lines" in forests, stripping trees bare of leaves below a certain height (the same effect modern giraffes have on acacia trees).

Yes - but only later in the dinosaur age. Flowering plants (called angiosperms) first appeared in the Early Cretaceous, around 130 million years ago, and gradually spread across the world. By the Late Cretaceous, magnolias, water lilies, and the ancestors of beech, oak, walnut, and maple were all present. Grass, however, was a late arrival - most of the Mesozoic had no grass at all. Tiny fragments of grass-like plants have been found in coprolites of Late Cretaceous sauropods from India, dating to around 67 million years ago. This means at least some sauropods did briefly munch on prehistoric grass before the asteroid wiped them out.

Some could, others couldn't. The big sauropods couldn't chew - they simply raked off leaves with peg-like teeth and swallowed them whole. By contrast, the duck-billed hadrosaurs and the horned ceratopsians were chewing champions. They had hundreds of teeth packed into dense "dental batteries" inside their cheeks. As old teeth wore down, new ones grew underneath to replace them - a single duck-bill like Edmontosaurus could carry up to 1,000 teeth at once, with new replacements ready for every position. These cheek teeth ground tough plants like a built-in milling machine.

Yes - or at least, some of them did. Smooth, polished stones called gastroliths ("stomach stones") have been found inside the rib cages of several sauropod skeletons, and these stones are common in birds today. The traditional explanation is that the dinosaurs swallowed stones to help grind up tough plants in the stomach, the way modern chickens use grit in their gizzards. However, this idea is debated - the relatively small number of stones found in most skeletons may not have been enough to grind much food. Some researchers now suggest much of the digestion was done by bacteria in the gut, the same way modern cows break down grass.

Hugely useful. A long neck let a sauropod stand still and reach an enormous volume of food without moving - saving energy that would be needed for the rest of its body. Brachiosaurus and its relatives held their necks high to reach treetops, while Diplodocus may have held its neck more horizontally to sweep through low-growing ferns and horsetails over a wide area. The likely ancestor of the sauropods, the prosauropod Thecodontosaurus, had a much shorter neck and walked on all fours - showing how this group started small before evolving in spectacular directions.

• As plant-eaters wore their teeth down on tough vegetation, new teeth grew up to replace them - a system shared with sharks and modern crocodiles.
• Edmontosaurus had about 1,000 teeth at any given moment, more than any other dinosaur known.
• Many of the plants that dinosaurs ate - ferns, ginkgos, conifers, cycads - still exist today, almost unchanged.
• The fish-eating marine reptile Elasmosaurus had a 7-metre (23-foot) neck, half its total body length - though it was a plesiosaur, not a dinosaur.
• Sauropods may have produced enormous amounts of methane gas through their digestion - in fact, some scientists have estimated their burps and farts could have contributed significantly to global temperatures in the Mesozoic.