The preservation of prehistoric life usually focuses on durable remains like bones, teeth, and shells. However, some of the most telling evidence about the behavior of extinct animals comes from the traces they left behind, such as footprints, burrows, and waste products. Paleontologists classify these as trace fossils because they record an animal’s activity rather than its anatomy. The preserved excrement transforms soft, organic material into geological specimens that offer a direct window into the diets and ecosystems of the deep past.
The Specific Scientific Term
The scientific term for fossilized feces, including that of dinosaurs, is “coprolite.” This name was coined in 1835 by the English geologist William Buckland, who was inspired by the findings of fossil hunter Mary Anning. The word itself is derived from the ancient Greek words kopros, meaning “dung,” and lithos, meaning “stone.”
A coprolite is formally classified as a type of trace fossil, which distinguishes it from a body fossil like a skeleton or a tooth. While a body fossil reveals the morphology and structure of an organism, a trace fossil provides direct evidence of the animal’s behavior, such as its diet. Coprolites are not strictly limited to dinosaurs; the term applies to the fossilized dung of any ancient animal, from fish and invertebrates to ancient mammals.
How Feces Becomes a Fossil
For soft organic material to survive the millions of years required for fossilization, a specific and immediate set of conditions must be met. Feces, which are full of microbes, typically decompose rapidly when exposed to oxygen and the elements. The first step in their preservation is rapid burial, where the waste is quickly covered by fine sediment, such as sand, mud, or volcanic ash.
This burial creates an anoxic, or low-oxygen, environment that slows the natural processes of decay. Mineral-rich groundwater begins to seep through the sediment and into the porous structure of the feces. A process called permineralization occurs, where dissolved minerals—most often calcium carbonate or silica—crystallize and replace the original organic material. The resulting coprolite is a dense, rock-like structure that retains the original shape and internal contents. Carnivore coprolites are often better preserved due to calcium phosphate from undigested bone fragments, which helps in the initial solidification process.
What Coprolites Reveal About Ancient Life
The true utility of coprolites lies in the detailed information they provide about prehistoric food webs and environments. By carefully slicing and examining the internal structure, paleontologists can determine the diet of the animal that produced it. For instance, the presence of crushed bone fragments, scales, or teeth points toward a carnivorous diet, while pollen, plant fibers, and seeds are clear indicators of a herbivorous one.
Microscopic analysis of pollen grains and plant cuticles preserved within the coprolite allows scientists to identify the specific flora present in the ancient habitat. This can offer insights into the types of plants available and even suggest whether a dinosaur was a selective forager. Coprolites can sometimes contain the eggs of ancient intestinal parasites, shedding light on the health, disease, and parasitic loads of prehistoric animals. This specialized field of study, sometimes called paleoscatalogy, offers unique data to reconstruct the complex relationships between organisms and their long-vanished ecosystems.