What Is a Coprolite?

A coprolite is fossilized feces. In plain English, it is fossil poop. The name comes from Greek words meaning "dung stone," which is an unusually direct description for a scientific term.

A tooth can tell us that an animal was equipped to slice meat. A coprolite containing fish scales or crushed bone can show what actually passed through its digestive system. That makes these fossils a useful companion to skeletons, teeth, footprints, and bite marks.

Coprolites are usually classified as trace fossils because they record an animal's activity. The bones, scales, and other meal fragments preserved inside them are body fossils. One small specimen can therefore contain two different kinds of fossil evidence. They also come from many animals besides dinosaurs, including fishes, crocodilians, mammals, and tiny invertebrates.

How Does Poop Become a Fossil?

Most droppings disappear quickly. They break apart, decay, or become food for other organisms. Fossilization requires some of that material to survive long enough for preservation to take hold. Burial by sediment can help protect it, while early mineral formation can preserve its shape and internal contents.

However, some fossilized digestive material was never pooped out. When an animal died, material still inside its digestive tract could become buried and fossilize along with the skeleton. Fossilized intestinal contents are more precisely called cololites, while coprolites are feces expelled from the body. This helps explain why Mary Anning found some of the material historically described as coprolites within the abdominal regions of ichthyosaur skeletons. Its position inside the animals was an important clue to its origin. (Knaust, 2020) (Kowinsky, 2025)

Many vertebrate coprolites are rich in calcium phosphate. The chemistry of the feces, microbial activity, and surrounding sediment can help minerals form before delicate remains are lost. This is why a coprolite may preserve tiny structures that are missing from ordinary fossils in the same bed. Preservation varies, though; fossil poop is not all made of one mineral. (Qvarnstrom et al., 2016)

There is also a useful distinction between mineralized coprolites and paleofeces, ancient dung preserved by drying, freezing, or other processes that retain more original organic material. Researchers sometimes use "coprolite" for both. Frozen Ice Age feces can preserve DNA, while a mineralized dinosaur coprolite records its contents in a very different way. (Murchie et al., 2026)

Mary Anning, William Buckland, and the Discovery of Coprolites

The story begins along the coast at Lyme Regis, England, where Mary Anning collected fossils from the Early Jurassic rocks of the Blue Lias and neighboring Lias beds. Among her finds were strange, stony lumps that local collectors called "bezoar stones." Some occurred in the abdominal region of ichthyosaur skeletons. (Kowinsky, 2025)

Anning had figured out what they were by about 1824. After breaking some open and finding fossil fish bones and scales inside, she realized they were fossilized ichthyosaur feces. She shared her observations and specimens with William Buckland, the Oxford geologist who often worked with her. A surviving letter records her collecting a basket full of coprolites and fossil cephalopod material for him to study. (Kowinsky, 2025) (Anning letter, ZSL Archives)

In 1829, Buckland described the fossils in his paper On the discovery of coprolites, or fossil faeces, in the Lias at Lyme Regis, and in other formations. He named them coprolites and explicitly credited Mary Anning. Fish remains, their association with ichthyosaur skeletons, and chemical evidence helped establish their origin. (Buckland, 1829)

These were not the first ancient droppings Buckland had studied. He had already examined fossil hyena dung from Kirkdale Cave, an Ice Age cave where the remains showed that animals such as hyenas had once lived in Britain. Anning's Lyme Regis discoveries extended the coprolite story deep into the Jurassic and helped turn peculiar beach finds into evidence of ancient diets and feeding relationships. (Duffin, 2009)

Buckland's Coprolite Table

Buckland took his interest in fossil dung beyond the laboratory. He had a table made with polished coprolites set into its top, turning specimens into an unusual piece of furniture. According to Lyme Regis Museum, it was probably made during a visit to Edinburgh in 1834, and its coprolites came from the Edinburgh area rather than Lyme Regis.

The polished pieces looked decorative enough to invite a guessing game before Buckland revealed what they were. The table is now part of the Lyme Regis Museum collection. It is a memorable reminder that fossil poop can look surprisingly attractive once cut and polished. (Lyme Regis Museum)

How Fossil Poop Helped Fertilize Victorian Farms

The agricultural potential of coprolites soon caught William Buckland's attention. In an 1847 letter to Henry De la Beche, an early paleontologist, friend of Mary Anning, and researcher of many of her fossils, Buckland wrote, "My coprolite paper is to go to the Agricultural Journal." By then, the phosphate content of coprolites had become increasingly important to agriculture. During the 1840s, John Stevens Henslow promoted phosphate-rich deposits, while fertilizer manufacturers developed ways to treat the material with sulfuric acid to make the phosphate more available to crops.

"Coprolite mining" spread through parts of eastern and central England, especially Suffolk and Cambridgeshire. However, much of the mined material was phosphate-rich nodules and fossil debris, not actual fossil dung. The commercial use of the word "coprolite" therefore became much broader than its paleontological meaning today.

The industry declined as accessible seams were depleted, digging became more expensive, and imported phosphate competed with local supplies. There was even a brief wartime revival. It would be misleading to say that every British coprolite deposit was mined out. Fossil coprolites still occur in Britain; the large commercial industry largely disappeared. (Ford and O'Connor, 2009)

Types of Coprolites: Spirals, Pellets, and Irregular Lumps

Coprolites can be grouped by shape, contents, preservation, or probable producer. These are overlapping descriptions: a single specimen might be spiral-shaped, phosphate-rich, and full of fish scales. Shape is a starting point, not a species label.

The distinction between spiral, scroll, and non-spiral forms often requires a look inside the fossil. Weathering can hide structures that a cut surface or scan reveals. (Rakshit et al., 2019)

Coprolites from Different Animals

Sharks and Other Fishes

Sharks have an internal intestinal valve that increases the surface available for digestion. It can help produce distinctive spiral or scroll-like fecal structures. Fossils may also contain scales, teeth, or bone from their meals. However, a spiral coprolite is not automatically shark poop: lungfishes and some other bony fishes also have spiral valves.

A scanned Triassic coprolite from Poland, for example, contained fish remains and broken shells. Researchers considered its likely producer to be a lungfish, Ptychoceratodus. The animals known from the site helped narrow the possibilities. (Qvarnstrom et al., 2017)

Crocodiles and Their Relatives

Miocene deposits along Calvert Cliffs, Maryland, preserve large coprolites attributed to crocodilians, including the marine crocodilian Thecachampsa. Some preserve tunnels made by other organisms after the dung was deposited, showing that even a dropping could become a small habitat or food source. (Godfrey et al., 2022)

An especially strange discovery from Calvert Cliffs involves coprolites with shark tooth impressions. The bites record contact with a shark, although whether it was investigating or trying to feed is uncertain. (Godfrey and Smith, 2010)

Cretaceous lag deposits across the southeastern United States also contain abundant crocodilian coprolites. Some of the larger ones may have been produced by the giant crocodilian Deinosuchus, the famous "supercroc," although that attribution remains tentative.

Dinosaurs

Dinosaur coprolites can reveal very different diets. One of the best-known examples is a large Canadian coprolite attributed to a tyrannosaur, most likely Tyrannosaurus rex, that contains abundant crushed bone (See the first image on this page). (Chin et al., 1998)

Plant-eating dinosaurs left surprises too. Late Cretaceous coprolites from Utah's Kaiparowits Formation contain decayed wood along with crustacean shell fragments, showing that at least some large herbivorous dinosaurs occasionally ate animal material. (Chin et al., 2017)

Ichthyosaurs and Jurassic Marine Food Webs

The classic Lyme Regis specimens associated with ichthyosaurs preserve fish remains and, in some cases, bones of smaller ichthyosaurs. These fossils helped early researchers such as Mary Anning and William Buckland recognize and describe coprolites, while also giving them new clues about how marine reptiles fed.

Mammals

William Buckland's research at Kirkdale Cave in England provided one of the earliest convincing examples of fossil dung. He realized that small rounded masses in the cave were fossilized hyena droppings and compared them with modern hyena dung, helping show that hyenas and other large mammals once lived in Ice Age Britain. (Duffin, 2009)

Much younger Ice Age droppings can preserve even more detail. Ground squirrel feces frozen in Yukon permafrost have yielded DNA from plants, microbes, and large mammals in the surrounding ecosystem, showing that the squirrels may have occasionally fed on carrion. However, not every DNA signal necessarily represents something the squirrel ate.

Invertebrates

Tiny fossil droppings can tell stories too. Pennsylvanian plant fossils preserve arthropod fecal pellets inside feeding tunnels, including larger pellets containing smaller pellets attributed to mites. This indicates that some tiny arthropods were feeding on another animal's dung. (Lakeram et al., 2026)

Not Everything That Looks Like Poop Is a Coprolite

Not every poop-shaped rock is a coprolite. Mineral concretions and other geological structures can form surprisingly convincing look-alikes, sometimes called pseudocoprolites. Iron-rich minerals such as siderite and goethite can even form rounded, lobed, or botryoidal shapes that resemble fossil feces. (Mustoe, 2025)

A famous auction specimen shows how easy it can be to get fooled. In 2014, a 1.04-meter (40-inch) specimen from Washington's Wilkes Formation was promoted as possibly the world's longest coprolite and sold for $10,370, including the buyer's premium. Later research on similar specimens from the formation identified them as siderite and goethite concretions rather than true coprolites. The auction specimen itself entered a private collection and could not be reexamined. (Mustoe, 2025)

So how do paleontologists tell the difference? Geological context is important, along with food remains such as bones, scales, shells, or plant material preserved inside. Many vertebrate coprolites are also phosphate-rich, although chemistry alone cannot prove that a specimen is fossil feces.

Why Scientists Study Fossil Poop

Coprolites connect animals to meals, parasites, and the organisms that recycled their waste. Different specimens answer different questions, and the strongest conclusions usually come from combining coprolites with other fossils from the same site.

Reconstructing Ancient Food Webs

One of the most important uses of coprolites is reconstructing ancient food webs. Bones and teeth establish which animals lived together, while meal remains preserved in coprolites can reveal direct feeding connections between them. A 2026 study of roughly 383-million-year-old Devonian coprolites from the Sula River site used X-ray scans to identify fish remains and reconstruct parts of an ancient lake food web. (Rebillard et al., 2026)

Finding Parasites

Microscopic eggs and other structures can preserve evidence of ancient infections. A Late Triassic coprolite from Thailand contained parasite eggs and cyst-like structures, including an egg assigned to an ascarid-type roundworm. Researchers proposed a crocodile-like phytosaur as a possible host, rather than identifying a definite dinosaur producer. (Nonsrirach et al., 2023)

Understanding Digestion and Decomposition

The condition of swallowed remains can help researchers investigate how food was broken down. Tunnels and smaller fecal pellets may record later visitors exploiting the dung. Separating the original meal from material added afterward is part of the detective work. (Godfrey and Smith, 2010) (Lakeram et al., 2026)

Looking Inside Without Breaking the Fossil

Thin sections reveal microscopic details but require cutting. CT and synchrotron scans can instead build three-dimensional views of internal remains, although their success depends on the specimen and imaging conditions. Chemical studies provide another line of evidence, and ancient-DNA methods apply to unusually well-preserved younger material. (Qvarnstrom et al., 2017) (Murchie et al., 2026)

What a Coprolite Cannot Tell Us

One dropping captures a limited feeding interval. It does not necessarily represent an animal's typical diet, every season of its life, or the habits of its whole species. Hard parts also survive digestion and fossilization more readily than many soft foods, so the preserved contents are an incomplete sample.

The producer and the contents are separate identification problems. A fish scale inside a coprolite identifies something swallowed, not the animal that swallowed it. Likewise, a parasite egg or a DNA sequence needs to be interpreted in context. The most useful descriptions explain both the evidence and the remaining uncertainty.

Five Fossil Poop Discoveries Worth a Closer Look

To show just how important fossil poop can be for understanding ancient animals, diets, and ecosystems, take a closer look at these five fascinating studies and what scientists discovered.

Fossil Feather Preserved Inside Tyrannosaur Poop

A feather inside a Late Cretaceous coprolite offers an unusual glimpse into a tyrannosaur's meal.

Ice Age Squirrel Poop

Squirrels ate mammoths, bison, and horses... sort of. Ancient DNA reveals a much more complicated story.

Devonian Fossil Poop

A 383-million-year-old food web reconstructed from fossil poop and preserved fish remains.

Triassic Fossil Poop Full of Parasites

More than 200 million years ago, one animal's droppings preserved evidence of several kinds of parasites.

When Plant-Eating Dinosaurs Ate Crustaceans

Wood and shell fragments reveal surprising dietary flexibility in large herbivorous dinosaurs.

References and Further Reading

Sources and Works Cited:

Kowinsky, J. (2025). The First Female Fossil Hunter: The Life and Legacy of Mary Anning. Pen & Sword History. ISBN: 9781399038560. View book on Amazon

The Geological Society of London. Coprolites, recognised 1824. https://www.geolsoc.org.uk/the-library/online-exhibitions/mary-anning-and-the-geological-society/pterosaurs-coprolites-and-sepia/coprolites/

Zoological Society of London Archives. Letter from Mary Anning to William Buckland: coprolites and sepias. https://zsl-archive.maxarchiveservices.co.uk/index.php/letter-from-mary-anning-to-william-buckland-2

Buckland, W. (1829). On the discovery of coprolites, or fossil faeces, in the Lias at Lyme Regis, and in other formations. Transactions of the Geological Society of London, Series 2, 3, 223-238. https://www.geolsoc.org.uk/the-library/online-exhibitions/mary-anning-and-the-geological-society/pterosaurs-coprolites-and-sepia/coprolites/

Bull, R., and Lyme Regis Museum (2013). History of Lyme in Museum Objects No. 11: Buckland's Coprolite Table. https://www.lymeregismuseum.co.uk/lrm/wp-content/uploads/2021/08/11_bucklands_-coprolite_-table_-reduced_-final.pdf

Ford, T. D., and O'Connor, B. (2009). A vanished industry: coprolite mining. Mercian Geologist, 17(2), 93-100. https://www.emgs.org.uk/uploads/1/4/9/1/149143154/mg17_2_2009_093_ford_oconnor_a_vanished_industry_-_coprolite_mining_1.pdf

Duffin, C. J. (2009). Records of warfare... embalmed in the everlasting hills: a history of early coprolite research. Mercian Geologist, 17(2), 101-111. https://www.emgs.org.uk/uploads/1/4/9/1/149143154/mg17_2_2009_101_duffin_a_history_of_early_coprolite_research_1.pdf

Knaust, D. (2020). Invertebrate coprolites and cololites revised. Papers in Palaeontology, 6(3), 385-423. https://doi.org/10.1002/spp2.1297

Mustoe, G. E. (2025). The Controversial Origin of Ferruginous “Coprolites”. Minerals, 15(12), 1271. https://doi.org/10.3390/min15121271

Qvarnstrom, M., Niedzwiedzki, G., and Zigaite, Z. (2016). Vertebrate coprolites (fossil faeces): An underexplored Konservat-Lagerstatte. Earth-Science Reviews, 162, 44-57. https://doi.org/10.1016/j.earscirev.2016.08.014

Rakshit, N., et al. (2019). First record of Mesozoic scroll coprolites: classification, characteristics, elemental composition and probable producers. https://doi.org/10.1111/pala.12409

Qvarnstrom, M., et al. (2017). Synchrotron phase-contrast microtomography of coprolites generates novel palaeobiological data. Scientific Reports, 7, 2723. https://doi.org/10.1038/s41598-017-02893-9

Chin, K., Tokaryk, T. T., Erickson, G. M., and Calk, L. C. (1998). A king-sized theropod coprolite. Nature, 393, 680-682. https://doi.org/10.1038/31461

Chin, K., Feldmann, R. M., and Tashman, J. N. (2017). Consumption of crustaceans by megaherbivorous dinosaurs: dietary flexibility and dinosaur life history strategies. Scientific Reports, 7, 11163. https://doi.org/10.1038/s41598-017-11538-w

Godfrey, S. J., et al. (2022). Coprolites from Calvert Cliffs: Miocene fecal pellets and burrowed crocodilian droppings from the Chesapeake Group of Maryland, U.S.A. https://riviste.unimi.it/index.php/RIPS/article/view/17064

Godfrey, S. J., and Smith, J. B. (2010). Shark-bitten vertebrate coprolites from the Miocene of Maryland. Naturwissenschaften, 97, 461-467. https://doi.org/10.1007/s00114-010-0659-x

Rebillard, A., et al. (2026). Investigating a Devonian vertebrate assemblage with synchrotron microtomography of coprolites. Scientific Reports, 16, 24728. https://doi.org/10.1038/s41598-026-63718-2

Murchie, T. J., et al. (2026). Ground squirrel coprolites preserve complex archives of ancient environmental DNA over 700,000 years. Nature Communications. https://doi.org/10.1038/s41467-026-72977-6

Lakeram, S. R., et al. (2026; published online February 5). Coprolite-filled borings: insight into the life history of detritivorous Pennsylvanian terrestrial arthropods. Journal of Paleontology, 99(6), 1369-1383. https://doi.org/10.1017/jpa.2025.10201

Nonsrirach, T., et al. (2023). First discovery of parasite eggs in a vertebrate coprolite of the Late Triassic in Thailand. PLOS ONE, 18(8), e0287891. https://doi.org/10.1371/journal.pone.0287891

Rummy, P., et al. (2021). The first record of exceptionally-preserved spiral coprolites from the Tsagan-Tsab Formation (Lower Cretaceous), Tatal, western Mongolia. Scientific Reports. https://doi.org/10.1038/s41598-021-87090-5