According to fossil evidence, some herbivorous dinosaurs occasionally fed on rotten wood. When white-rot fungus decomposes wood, tough lignin tissues break down and it becomes soft, stringy, and digestible. The main source of nutrition, however, is the large amounts of small animals that make their home in rotten wood. Shell fragments of crabs found in coprolites support the theory that herbivorous dinosaurs, like modern animals, had small amounts of meat in their diet as a source of certain minerals such as calcium.
Rotten Wood being preferred by hadrosaurs and ceratopsians may be a reference to a 2017 study that found rotten wood tissue and crab shells in hadrosaur coprolites.