Unleashing floods: Researchers learn more about how fossils form

MINNEAPOLIS / ST. PAUL (01/12/2026) — A new study by researchers at the University of Minnesota Twin Cities challenges previous classifications paleontologists use to determine how the fossil record is formed. They investigated how dinosaur and mammal bones are transported and buried by floodwaters to understand how the remains of animals might disperse prior to being buried and becoming fossils.

The research provides new clues for understanding animal extinction and environmental changes. The paper was recently published in Paleobiology, a peer reviewed journal. 

Researchers tested bone movement under unsteady flow dynamics, such as those found in natural sheet floods. These are frequently invoked as agents of dispersal in paleontological literature, but differ significantly from the typical river flow conditions used in decades-old original transport experiments. Previously, flood events were often used to explain the burial of animals, but the details of these events have not been explored, until now.

“Paleontologists try to piece together the stories of how fossil sites actually came to be, sort of CSI style,” said Michael Chiappone, a University of Minnesota Ph.D. candidate and the lead author of the study. “So we asked ourselves: ‘Are fossil organisms preserved in the places where they died? Or are we finding them after they’ve been moved some distance after death by scavengers or water flow?’”

Using the unique facilities at the University of Minnesota’s St. Anthony Falls Laboratory, the team reproduced surging waves of water that simulated real-world floods and river features like ripples, dunes and bars in a set of full scale experiments. From these tests they were able to determine how bones sort in water flow by their sizes, shapes and densities.

Heavy elements like articulated skulls barely moved, while others, such as hip bones, tended to move further, and even leave the experimental area. The overall data suggests that in typical seasonal floods, many bones don't move far from where the animal died, unless the flood was extremely powerful or the bones were very small. 

By recreating real flood conditions, the study shows that how water moves and interacts with the riverbed can sort bones in ways that don’t always match the traditional system, called the Voorhies classification, used to predict which bones should be carried away most easily by flowing water.

This new information encourages paleontologists to look for additional variables when reconstructing extinct animals and the environments they lived in. 

“The results from our experiments will help us better interpret how bones were sorted, accumulated and buried at paleontological sites we excavate,” said Peter Makovicky, a professor and paleontologist in the University of Minnesota Department of Earth and Environmental Sciences and senior author on the paper. “This provides the basic information we work back from to reconstruct extinct animals and the environments they lived in.”

The team has already conducted further experiments on a wide variety of bones and are looking to expand this research to include extremely large bones found in elephants, whales and bison. 

In addition to Chiappone and Makovicky, the research team included Michele Guala, professor in the University of Minnesota Department of Civil, Environmental, and Geo- Engineering and St. Anthony Falls Laboratory; and Raymond Rogers from Macalester College. 

Read the full paper entitled, “When the Levee Breaks: Experimentally Testing Dinosaur and Mammal Bone Transport in Unsteady Flows” on the Paleobiology website.