Large Herbivorous Dinosaurs Were Snacking On Crustaceans


Hadrodaurs were thought to be plant-eaters, but it seems they also chowed down on crabs and crayfish. Filippo onez Vanzo/Shutterstock

Herbivorous dinosaurs tended to eat, well, plants. But the fossilized poop of these animals has revealed something unusual – it now seems these big beasts occasionally branched out gastronomically and also snacked on crayfish and crabs.

The unusual behavior was brought to light when researchers uncovered the 75-million-year-old fossilized poop, known as coprolites, of some large herbivorous dinosaurs, which is itself quite a rare discovery. While carnivore coprolites are fairly common as the bones and minerals in them help in the preservation process, the poop of plant-eating dinosaurs is far scarcer.


In the Grand Staircase-Escalante National Monument in southern Utah, scientists found what they believe to be the poop of herbivorous hadrosaurs, also known as duck-billed dinosaurs. To their surprise, hidden within 10 of these turd nuggets, they discovered tiny little pieces of shell. While they were unable to identify what crustacean they once belonged to, the scientists report in their paper in Scientific Advances that they previously found the remains of crabs fossilized at the same site.

The bits of shell were found in the poop among pieces of decaying wood, which the hadrosaurs were also apparently chowing down on. One suggestion is that perhaps the animals were eating the wood and hoovering up the assorted insects and crustaceans with it by accident. However, according to the researchers, this seems unlikely.  

The bits of shell indicate that the crustaceans were at least 5 centimeters (2 inches) in length, and possibly even larger than that. If this were the case, depending on the size of the dinosaur, the crabs or crayfish would have been around 20 to 60 percent of the width of the animals’ mouth, meaning that it would have been a bit of a stretch to eat something that size by accident, particularly if it was squirming about.

“While it is difficult to prove intent regarding feeding strategies, I suspect these dinosaurs targeted rotting wood because it was a great source of protein in the form of insects, crustaceans and other invertebrates,” remarks co-author Karen Chin, associate professor at the University of Colorado Boulder, in a statement.


This then raises the question of what a predominantly plant-eating animal was doing snacking on hard-shelled critters every so often. The fact that it was not found within just one coprolite suggests that this was a fairly common behavior among some of these animals, and Chin postulates that it might have occurred during breeding season, with the boost of protein and calcium aiding in the development of eggs.

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