This news article is based on the open-access journal article (Chin, Feldmann and Tashman, 2017) published in Scientific Reports. The article is published under a Creative Commons Attribution 4.0 license. Figure 1 in the original paper contains third-party material and is specifically excluded from that license, so it is not reproduced here.
Summary points about the dinosaur poop study:
- Age: Late Cretaceous, about 76.0 to 74.1 million years ago
- Location: Kaiparowits Formation, southern Utah
- Material: More than 15 large coprolite deposits preserved at several stratigraphic levels
- Main food: Fungus-decayed conifer wood
- Surprise ingredient: Crustacean cuticle occurred in at least 10 of 15 examined coprolite deposits
- Possible producers: Large herbivorous dinosaurs, especially hadrosaurs or ceratopsians
- Big idea: Some herbivorous dinosaurs probably shifted diets seasonally and accepted animal foods when they were useful
Introduction: Apparently the Salad Bar Had Shellfish
Apparently, being a plant-eating dinosaur did not always mean sticking strictly to the salad bar.
A remarkable collection of Late Cretaceous coprolites from southern Utah is packed with chewed-up, fungus-rotted conifer wood. That alone is unusual. Mixed into many of those fossilized fecal masses are fragments of thick, mineralized crustacean shells and appendages.
The fossils do not show giant herbivores turning into active meat hunters. They show something more believable and more interesting: flexible feeding behavior in dinosaurs that were still fundamentally plant eaters.
A Cretaceous Floodplain Full of Dinosaurs
The coprolites come from the Kaiparowits Formation of southern Utah. These rocks were deposited roughly 76.0 to 74.1 million years ago on a broad alluvial plain crossed by meandering rivers, ponds, and wet lowlands.
Researchers documented more than 15 coprolite deposits from at least three stratigraphic levels, with sites spread across roughly 20 kilometers. Some deposits were large blocky masses, and others appear to represent repeated defecation events. In other words, this was not one dinosaur having one strange lunch.
The formation also preserves a rich dinosaur fauna. Hadrosaurs are particularly common and include Parasaurolophus and species of Gryposaurus. Ceratopsians, ankylosaurs, nodosaurs, pachycephalosaurs, and other ornithischians are present as well.
Who Left the Giant Pile?
No dinosaur skeleton was found with a convenient sign saying "this one did it," so the exact producer cannot be identified. Coprolites are trace fossils: evidence of what an animal did, not part of the animal itself.
The enormous size of the fecal masses and their heavily processed plant contents point toward large herbivorous dinosaurs with teeth capable of breaking down fibrous food. The authors identify large hadrosaurs and ceratopsians as good candidates. Hadrosaurs may be especially plausible because their complex dental batteries could crush and grind a broad range of plant tissues.
So "hadrosaur poop" is tempting shorthand, but the scientifically careful description is coprolites produced by large herbivorous dinosaurs, probably hadrosaurs or ceratopsians.
First Course: Rotten Wood
Thin sections show that most of the coprolites consist of broken conifer wood and loose wood cells called tracheids. The microscopic structure also records decay by white-rot fungi before the wood was swallowed.
That matters because white-rot fungi break down lignin, one of the compounds that makes wood tough and resistant to digestion. The dinosaurs were therefore not gnawing on fresh, hard logs. They were eating wood that fungi had already softened and chemically altered.
Modern studies cited by the authors show that fungal decay can dramatically increase the digestibility of wood. The decaying logs would also have contained fungal tissues and small animals, turning a rotten log into something closer to a nutrient-rich feeding patch.
Then Scientists Found the Shells
At least 10 of the 15 examined coprolite deposits contained dark, shell-like fragments. Some were flat or gently curved; others formed tubular pieces that looked like sections of appendages.
The researchers compared thickness, surface texture, internal lamination, mineral composition, and the geometry of the fragments. The combination fits crustacean cuticle: the hard outer covering of animals such as crabs and their relatives.
Some fragments were substantial. One measured about 2 by 3 centimeters, and the authors conservatively estimated that the original crustaceans had a minimum dimension of roughly 5 centimeters. These were not microscopic specks that could be dismissed as accidental grit.
The exact crustacean is unknown. Fossil crab claws occur in slightly older nearby formations, but the remains inside the coprolites are not diagnostic enough to call them crabs with confidence. "Sizeable crustaceans" is the safer description.
Did the Dinosaurs Mean to Eat Them?
That is the tricky part. Fossils rarely preserve intention.
The authors considered three possibilities: active hunting, deliberate feeding on rotten logs that happened to be rich in invertebrates, or accidental swallowing while eating plants. The repeated occurrence of sizeable crustacean fragments at different sites and stratigraphic levels makes pure accident less convincing.
The favored middle-ground explanation is that dinosaurs targeted rotting wood as a resource patch and accepted the crustaceans living in it as useful or desirable food. They may not have been stalking crabs across the floodplain, but they probably were not carefully spitting them out either.
Protein, Calcium, and a Possible Breeding-Season Snack
Crustacean soft tissues would have provided high-quality protein, while their mineralized cuticle offered calcium. Fungal tissues in the decayed wood would have added still more nutrients.
The researchers argue that this probably was not a year-round diet. Leaves and other plant tissues would normally have been more abundant and renewable than woody material. Instead, the coprolites may record a seasonal dietary shift.
One intriguing possibility is that extra protein and calcium were especially useful during reproduction and egg laying. The paper presents this as a plausible life-history explanation, not a proven behavior.
Why This Changes the Picture of Herbivorous Dinosaurs
Modern herbivores are not always as strict as the labels suggest. Many plant-eating birds consume insects or other animal foods when the opportunity or nutritional need arises.
Because birds are living dinosaurs, the researchers suggest that dietary flexibility in modern birds may be a useful comparison for large non-avian dinosaur herbivores. Their teeth and jaws were adapted for plants, but that does not mean every mouthful was botanically pure.
The study does not turn hadrosaurs into carnivores. It shows that a "herbivorous dinosaur" could still be opportunistic enough to eat rotting wood, fungi, and sizeable crustaceans when the menu made sense.
Sometimes fossil poop does more than tell us what an animal ate. It reminds us that extinct animals were living organisms with flexible behavior, not labels in a textbook.
Journal Article:
Chin, K., Feldmann, R. M., & Tashman, J. N. (2017). Consumption of crustaceans by megaherbivorous dinosaurs: dietary flexibility and dinosaur life history strategies. Scientific Reports, 7, 11163. Published September 21, 2017. https://doi.org/10.1038/s41598-017-11538-w.
Image and reuse license: The article is published under the Creative Commons Attribution 4.0 International License. Figure 1 is specifically excluded from that license in the original paper and should not be reused without separate permission.
FAQs: Dinosaur Poop, Rotten Wood, and Crustaceans
Quick answers about the Kaiparowits coprolites and what they reveal about dinosaur diets.
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Did plant-eating dinosaurs really eat crustaceans?
Yes. Crustacean cuticle was found repeatedly inside large Late Cretaceous coprolites attributed to large herbivorous dinosaurs. The exact dinosaur species is unknown, but hadrosaurs and ceratopsians are strong candidates.
See: Scientists Found the Shells -
Were the dinosaurs eating crabs?
Possibly, but the fossils are not diagnostic enough to identify the crustaceans as crabs. The study safely identifies them as sizeable crustaceans.
See: Crustacean Evidence
- How old are the dinosaur coprolites?The coprolites come from the Kaiparowits Formation of southern Utah, deposited roughly 76.0 to 74.1 million years ago during the Late Cretaceous.
- Which dinosaurs may have produced the coprolites?Large hadrosaurs and ceratopsians are the strongest candidates. Hadrosaurs may be especially plausible because their dental batteries were well suited to crushing and grinding fibrous plant material.
- Why were the dinosaurs eating rotting wood?The wood had been degraded by white-rot fungi before it was eaten. Fungal decay removed some lignin and may have made the remaining cellulose-rich wood easier to digest.
- How common were crustacean remains in the coprolites?At least 10 of 15 examined coprolite deposits contained fragments interpreted as crustacean cuticle.
- How large were the crustaceans?One preserved shell fragment measured about 2 by 3 centimeters. The researchers conservatively estimated that the crustaceans themselves had a minimum dimension of roughly 5 centimeters.
- Were the crustaceans eaten accidentally?Accidental ingestion cannot be completely excluded, but the repeated occurrence of sizeable crustacean remains at different sites and stratigraphic levels suggests that the dinosaurs accepted or deliberately exploited them as food.
- Why might animal food have been useful to herbivorous dinosaurs?Crustacean tissues would have supplied protein, while their mineralized cuticle supplied calcium. The authors proposed that periodic consumption may have been especially useful during breeding and egg production, although this remains a hypothesis.
- Does this mean herbivorous dinosaurs were really carnivores?No. The evidence suggests dietary flexibility, not a meat-based lifestyle. These dinosaurs were primarily plant eaters that may have opportunistically consumed animal foods.
Jump to Sections
Key Facts | Introduction | Kaiparowits Formation | Who Made It? | Rotten Wood | Crustaceans | Accident or Intentional? | Nutrition | Why It Matters | Journal Article | FAQs
