"None of the fossils of the earliest mammals have the sort of exceptional preservation that includes stomach contents to infer diet, so instead we used a range of new techniques which we applied to our fossil finds of broken jaws and isolated teeth," study lead author Pamela Gill, a research associate in the School of Earth Sciences at the University of Bristol, in the United Kingdom, said in a statement. "Our results confirm that the diversification of mammalian species at the time was linked with differences in diet and ecology."
By examining the microscopic scratches and pits in the fossilized teeth, Gill and her colleagues determined that Morganucodonconsumed mostly harder and crunchier bugs like beetles, while Kuehneotheriumpicked softer insects like scorpion flies. This same technique is used to examine the teeth of present-day bats that feed on insects.
"This is the first time that tooth wear patterns have been used to analyze the diet of mammals this old," Mark Purnell, a professor of palaeobiology at the University of Leicester, in the U.K., said in a statement. "That their tooth wear compares so closely to bats that specialize on different kinds of insects gives us really strong evidence that these early mammals were not generalists when it came to diet, but were quite definite in their food choices."