Scientists have just made a remarkable find: a 13-million-year-old ape skull that is so well preserved, scientists were able to see its unerupted teeth and the impression its brain left. The skull was discovered in northern Kenya, and researchers think it belonged to an infant ape that died in a forest, with its body blanketed by ash from a nearby volcano.

The skull is the best preserved of its kind ever found, and provides an important and rare look into the stages of ape evolution.

“We’ve been looking for ape fossils for years—this is the first time we’re getting a skull that’s complete,” says Isaiah Nengo, the De Anza College anthropologist who led the discovery, according to a National Geographic report.

The skull is only about the size of a lemon and belongs to the species Nyanzapithecus alesi.

“The discovery in Kenya of a remarkably complete fossil ape skull reveals what the common ancestor of all living apes and humans may have looked like,” a statement from the Leakey Foundation reads. “The find, announced in the scientific journal Nature on August 10th, belongs to an infant that lived about 13 million years ago. The research was done by an international team led by Isaiah Nengo of Stony Brook University-affiliated Turkana Basin Institute and De Anza College, U.S.A.”