Fossil dung is more than an unusual curiosity. A coprolite can preserve food fragments, chemistry and the work of other organisms that used it after it was deposited. In some Cretaceous examples, small tunnels and chambers occur inside fossilized herbivore dung. Researchers have interpreted these traces as possible insect activity, including that of dung beetles. The association is intriguing, but a burrow does not come with a label naming its maker.
What is a coprolite?
A coprolite is fossilized animal excrement. It is a trace fossil because it records an activity rather than the body of the animal that produced it. Coprolites may contain plant fibres, bone fragments, scales, pollen or small invertebrates. Those inclusions can reveal diet or the food web, but first researchers must establish that the object is genuinely dung and not a mineral concretion or another sedimentary structure.
Identifying the producer is often harder. A coprolite found close to a skeleton may belong to that animal, but proximity alone is not proof. Size, shape, internal structure and contents can narrow the options. In some sites, repeated associations and distinctive digestive anatomy strengthen an attribution. Even then, scientists may identify a broad group rather than a particular species. The evidence in coprolites and gut contents is powerful precisely because its limits can be tested.
Tunnels inside ancient dung
Some Cretaceous coprolites preserve galleries that pass through the dung mass. Their position suggests that the material was colonized while it remained accessible, rather than being a later crack through surrounding rock. Researchers compare the size, branching pattern and arrangement of tunnels with traces made by living insects. Such comparisons can support an insect interpretation, but several kinds of small invertebrates can make superficially similar galleries.
One hypothesis is that insects used herbivore dung as food or a nursery. Modern dung beetles roll, bury or tunnel through dung, and their larvae develop in nutrient-rich material. This living behaviour provides a useful comparison, not a direct template for the Cretaceous. The trace fossil does not necessarily show a modern scarab beetle, and the insect may have consumed, nested in or simply moved through the material.
Did dinosaurs and dung beetles interact?
A 2016 study examined fossil and molecular evidence to ask whether scarab dung beetles evolved in association with dinosaurs. It discussed Cretaceous traces within dinosaur coprolites but noted that dating and identifying the beetle lineages are difficult. A later review of fossil dung beetles argued that some early fossils previously assigned to the dung-beetle group are uncertain. In 2023, a study of beetle gut contents showed that living dung beetles can feed broadly on reptile dung, making it possible that ancient beetles used dinosaur waste without proving that they did.
This debate separates three claims that are easy to conflate: a coprolite contains a tunnel; an insect made the tunnel; and a particular beetle lineage evolved by feeding on dinosaur dung. The first may be observed directly. The second is an interpretation based on trace shape and context. The third requires independent chronological, anatomical or molecular evidence. A direct association between two fossils cannot by itself establish the evolutionary origin of a whole insect group.
A small trace of a larger ecosystem
Dung connects large herbivores to insects, microbes and soil. Removing waste from the surface and moving organic matter underground can affect nutrient cycling in modern environments. We should not assume the same ecological effects or beetle communities existed in the Mesozoic, but fossil traces show that animal waste attracted other organisms and became part of ancient food webs.
The safest reading is both modest and interesting: fossilized dinosaur dung can preserve evidence of organisms that interacted with it, and some tunnels may record insect use. Their exact maker and behaviour remain uncertain in individual cases. Careful descriptions of trace geometry and geological setting allow new finds to refine that picture without turning a plausible comparison into a settled identification.
Frequently asked questions
What is a coprolite?
A coprolite is fossilized animal excrement. It is a trace fossil that can preserve food remains and evidence of later activity.
Do tunnels in dinosaur dung prove dung beetles made them?
No. Their shape may be consistent with insect activity, but a trace alone does not identify its maker as a modern-style dung beetle.
Did dung beetles evolve by feeding on dinosaur dung?
That remains debated. Fossil associations and molecular dates do not yet establish a simple origin story linking a whole beetle lineage to dinosaurs.
Can researchers tell which animal produced a coprolite?
Sometimes they can narrow it using size, shape, contents and context, but the producer is often uncertain, especially when fossils are isolated.