UMass Amherst news office has a release on a study looking at bats skulls:

“This study conducted during the International Year of the Bat offers a clear example of how the evolution of new traits, in this case a skull with a new shape, allowed animals to use new resources and eventually, to rapidly evolve into many new species,” (Elizabeth) Dumont (of UMass) says. “We found that when a new ecological niche opened up with an opportunity for bats that could eat hard fruits, they shifted their diet significantly, which in turn led to the evolution of new species.”

The skulls and faces of a nectar-eating bat (left) an insect-eating bat (middle) and a fruit bat (right). The short skulls of fruit bats allow them to bite harder than nectar or insect-eating bats.

Photos courtesy of Elizabeth Dumont, University of Massachusetts Amherst