Among the least common but most informative fossils are fossilized dung, technically known as coprolites. Formed only under extremely favorable conditions, they frequently retain remnants of tough food items such as bones or wood fragments. Coprolites from herbivorous dinosaurs are usually full of conifer needles and wood from twigs. An accumulation of coprolites from Utah, USA shows something completely unexpected: rotten wood and crustacean shells!
In September 2017, paleontologists Karen Chin, Rodney Feldmann, and Jessica Tashman described the coprolite accumulations from the Kaiparowits Formation in Utah and compared them to previously described coprolites from the Two Medicine Formation in Montana. The new location yielded several different specimens from roughly the same area, but in different layers of sediment.
Both sites date from the Late Cretaceous Period, about 75-80 million years ago and had similar herbivorous dinosaurs: large duck-billed hadrosaurs and horned ceratopsians, as well as a variety of much smaller plant-eaters. The coprolites are far too large to be from anything other than hadrosaurs or ceratopsians, and Chin, Feldmann, and Tashman considered hadrosaurs to be the only possible producers. Although ceratopsians have strong jaws and teeth, only hadrosaurs have teeth capable of pulverizing wood.