This is Alesi, the skull of the new extinct ape species Nyanzapithecus alesi (KNM-NP 59050).

A group of scientists have found what may be the most intact fossilized primate skull ever discovered, and the find could shed light on the common evolutionary heritage shared by apes and humans.

The lemon-sized skull was discovered in Kenya by an international team of researchers, and was dated to the middle of the Miocene era, a little-understood time when many species of ape arose in Africa, including common ancestors of both modern apes and humans.

This skull could give scientists insights into what those common ancestors looked like.

The team reported its findings Wednesday in the journal Nature.

The fossil, belonging to the newly named species Nyanzapithecus alesi, bears some resemblance to those of modern-day gibbons, and possesses features that would only be found in apes, such as ape-like teeth. However, certain features distinguish it from modern gibbons, suggesting it was a very different type of animal.

"Gibbons are well known for their fast and acrobatic behavior in trees," said Fred Spoor of University College London and the Max Planck Institute for Evolutionary Anthropology, in a press release. "But the inner ears of Alesi show that it would have had a much more cautious way of moving around."

The team used an extremely sensitive form of 3-D X-ray to peek inside the skull, revealing information that led them to conclude the skull belonged to an infant one to four months old when it died. Volcanic ash found around the fossil suggests it may have died during an eruption, but researchers cannot be sure.

Scientists estimate the Miocene period, which spanned from 5 million to 25 million years ago, produced more than 40 different species of hominoids — a term for a superfamily of primates that includes apes, humans and related ancestral species.

It is extremely uncommon to find fossil primate skulls, especially those belonging to apes.

"Importantly, the African fossil record lacks any reasonably complete hominoid crania between 17 and 7 million years ago, and no cranial specimens are known at all from between 14 and 10 million years, greatly hampering the analysis of hominoid evolution," the researchers said in their study.

The study was sponsored by The Leakey Foundation and trustee Gordon Getty, the Foothill-De Anza Foundation, the Fulbright Scholars Program, the National Geographic Society, the European Synchrotron Radiation Facility and the Max Planck Society.

Scientists will need to study the skull further, but can already draw a few conclusions.

"What the discovery of Alesi shows," said lead author Isaiah Nengo, a professor of anthropology at De Anza College in California and Stony Brook University in New York, in a news release, "is that this group was close to the origin of living apes and humans and that this origin was African."