A new study by the University of Minnesota 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 study, published in Paleobiology, tested bone movement under unsteady flow dynamics, such as those found in floods. Previous research relied on steady-state flow conditions, which differ significantly from how water moves in a natural flood.
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. From these tests they were able to determine how bones in water flow by their sizes, shapes and densities. They found:
- Heavy elements like skulls barely moved while others, such as hip bones, tended to move further.
- 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 simulating actual flood conditions, the researchers found that factors like flow dynamics and interactions with the environment lead to bone movement that does not always align with previous research methodologies.
"Paleontologists try to piece together the stories of how fossil sites actually came to be, sort of CSI style," said Michael Chiappone, a Ph.D. candidate in the College of Science and Engineering and 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?'"
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 College of Science and Engineering 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. Future research will 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 College of Science and Engineering and St. Anthony Falls Laboratory, and Raymond Rogers from Macalester College.
Research was funded by the Nels Nelson Memorial Fellowship and the Frederick M. Swain Memorial Fellowship.
About the College of Science and Engineering
The University of Minnesota College of Science and Engineering brings together the University's programs in engineering, physical sciences, mathematics and computer science into one college. The college is ranked among the top academic programs in the country and includes 12 academic departments offering a wide range of degree programs at the baccalaureate, master's, and doctoral levels. Learn more at cse.umn.edu.
