Why a Dinosaur Ate Rotten Wood on Purpose

PALEODEX · 8 August 2026 · 5 min read

Not every dinosaur coprolite story is about a predator crushing bone. One of the strangest diets in the fossil record belonged to a plant-eater.

We've already told the bone-crushing side of this story: in 1998, Karen Chin described a T. rex coprolite packed with the crushed bone of a young plant-eater — read that one here. But the most surprising coprolite diet in the record doesn't belong to a predator at all. It belongs to a duck-billed dinosaur that seems to have eaten rotten wood on purpose.

A hadrosaur's very odd lunch

In 2007, Karen Chin published a study of coprolites attributed to Maiasaura peeblesorum, a hadrosaur — a duck-billed, plant-eating dinosaur — from the Upper Cretaceous Two Medicine Formation of Montana. Inside them, she found fragments of wood that had been extensively broken down by fungal decay before the animal ate it, alongside crustacean remains. That's not an accident of preservation: the pattern showed up repeatedly, across multiple coprolites, which is exactly the kind of evidence that turns "huh, weird" into a real behavioral finding.

Why eat rotten wood on purpose?

Wood is mostly cellulose and lignin, both notoriously hard for most animals to digest — that's why termites rely on gut microbes to do the work for them. Fungal decay changes the equation: fungi break wood down before it's even eaten, softening the structure and, in the process, concentrating protein-rich fungal tissue inside it. Chin's interpretation was that Maiasaura deliberately targeted rotting logs as a source of protein and easier-to-digest carbohydrate, alongside whatever crustaceans were also living in the decaying wood. It's the same basic strategy some living animals use — just documented, for once, in a 75-million-year-old bathroom break.

Reading a coprolite's ingredients

This is also a good illustration of how paleontologists can often tell herbivore and carnivore coprolites apart before they even look inside. Carnivore coprolites, like the T. rex specimen above, tend to preserve as calcium phosphate — the ingested bone and soft tissue are naturally phosphorus-rich, which drives that mineral replacement. Herbivore coprolites more often fossilize via silica or calcium carbonate instead, and their contents skew toward plant fragments, phytoliths, and — as it turns out — the occasional mouthful of fungus-softened timber.

Why this is exactly what we built PaleoDex for

A hadrosaur eating rotten wood for the fungus inside it is exactly the kind of real, slightly absurd, thoroughly documented detail that never makes it into a stylized dinosaur game. It's in the actual fossil record because someone looked closely at fossilized dung instead of skipping past it. Browse the herbivores and carnivores side by side in the Fossil-DEX, or read how paleontologists prove a coprolite is real in the first place.

Sources

A dinosaur's rotten-wood diet, and the specimen that inspired the header image — sources below.

• The Paleobiological Implications of Herbivorous Dinosaur Coprolites from the Two Medicine Formation: Why Eat Wood? — Chin, PALAIOS (2007)
• "Barnum" coprolite specimen record — Poozeum