Fossil shells point to bigger predators picking on small prey

The drill holes left in fossil shells by hunters such as snails and slugs show marine predators have grown steadily bigger and more powerful over time but stuck to picking off small prey, rather than using their added heft to pursue larger quarry, new research shows.

The study, published today in Science, found the percent of shell area drilled by predators increased 67-fold over the past 500 million years, suggesting that the ratio of predatory driller size and tough-shelled prey increased substantially.

“These drill holes track the rise of bullies: bigger, stronger predators hunting the same size prey their much smaller predecessors did,” said Michal Kowalewski, the Jon L. and Beverly A. Thompson Chair of Invertebrate Paleontology at the Florida Museum of Natural History at the University of Florida and a study co-author. “What’s exciting about this project is that we found a drilled fossil shell can tell us both the size of the prey and the size of the predator that ate it.”