In today’s Academic Minute, Dr. Greg Wilson of the University of Washington reveals how a slight change in tooth shape allowed early mammals to compete in a world dominated by dinosaurs.
Greg Wilson is an assistant professor of biology at the University of Washington and Adjunct Curator of Vertebrate Paleontology at the university’s Burke Museum of Natural History and Culture. His research interests include the mass extinction associated with the Cretaceous-Tertiary (K-T) boundary, paleobiogeography, and using high-resolution imaging to compare the teeth of early mammals. He holds a Ph.D. from the University of California, Berkeley.
Dr. Gregory Wilson, University of Washington – Success of Early Mammals
For many years scientists believed that during the age of dinosaurs mammals were mostly small creatures that faced an everyday battle just to survive. But our recent research shows that at least one mammal group --- small rodent-like creatures called multituberculates… or multis --- actually did quite well during the last 20 million years of the reign of dinosaurs.
Though multis survived the calamity that killed off the dinosaurs 66 million years ago… eventually they were out-competed by other mammals and they too died out. But the reason multis did so well competing with dinosaurs is that some developed numerous bumps… or cusps… on their back teeth. That allowed them to survive by eating flowering plants that were coming into their own around that time. The bumps on their teeth were ideal for grinding plant matter to a pulp for easy digestion.
Our team examined teeth from 41 species of multis from fossil collections around the world. We analyzed detailed three-dimensional models of the teeth in very high resolution. Around 140 million years ago, multis had large blade-like teeth at the front of their mouths… which is great for meat- and insect-eaters. But we found that they also were beginning to develop more complex teeth toward the back of their mouths… perfect for grinding plants. We saw that over millions of years… in some multis those blade teeth in front got smaller and less important… while the teeth in back became better adapted for crushing plant material.
The events that killed off the dinosaurs apparently didn't have as much of an impact on the flowering plants. That meant that --- thanks to the evolution of their teeth --- the multis had plenty of food sources to survive long after the dinosaurs were gone.