The Cretaceous-era ant — Ceratomyrmex ellenbergeri — was trapped while feasting on a Caputoraptor elegans, an extinct forerunner of the cockroach. The fossil was discovered in Myanmar. The prehistoric meal is newly described by an international team of researchers in the journal Current Biology.

It’s rare to find animal behavior preserved in fossil form, and the find confirmed a theory about how hell ants ate. The insects apparently fed using sharp jaws that moved up and down, unlike their modern counterparts, whose jaws move horizontally.

Using evidence from the amber-trapped predator and its prey, the team confirmed that hell ants were one of the earliest types of ant. They compared the specimen’s sharp jaws to the predatory features of other ancient hell ants, whose headgear included different variations of jaws and even long horns thought to be used to impale prey.

Though it’s unclear how ants abandoned the weird jaws of their long-lost kin over time, the researchers think the variety of different predatory features represent adaptations that were eventually lost as the insects evolved.

“This fossil reveals the mechanism behind what we might call an ‘evolutionary experiment,’ ” said Phillip Barden, assistant professor at the New Jersey Institute of Technology’s department of biological sciences who led the study, in a news release.