Cranial bones of three primitive horned dinosaurs have been found in a Lower Cretaceous stratum in Sasayama, Hyogo Prefecture, the Museum of Nature and Human Activities said Saturday.

Noting that the ages of the dinosaurs are different, the prefectural museum hopes that the bones can clarify the developmental process of the species.

In 2009, fossils found in the same layer were Japan’s first confirmed discovery of the skull bones of a horned dinosaur believed to be a neoceratops.

This time, a total of 16 bone fossils were found, including upper and lower jaws, dentary bones and backbones 2 millimeters to 9 centimeters in length, the museum said.

Unique lines on a tooth surface suggest the fossils are from neoceratops — related to the more well-known triceratops — the museum said, adding that size differences in the bones indicate the dinosaurs were not the same age. The largest of the three was about 1 meter long and one was not an adult, the museum added.

“Cranial bones tell a lot,” said Haruo Saegusa, chief researcher at the museum. “These bones are expected to help us understand how the dinosaurs lived.”

KEYWORDS fossils, dinosaurs