This is the first record of an ancient owl being active during the day.

The research team led by Li Zhiheng and Thomas Stidham from the Institute of Vertebrate Paleontology and Paleoanthropology under the Chinese Academy of Sciences named the species Miosurnia diurna in reference to its close living relative, the diurnal Northern Hawk Owl.

The fossil skeleton was found in rocks deposited at an elevation greater than 2,100 meters in the Linxia Basin of China's Gansu Province, at the edge of the Qinghai-Tibetan Plateau, according to the study.

The fossil preserves nearly the entire skeleton from the tip of the skull through the wings and legs to the tail bone, along with body parts that are rarely seen as fossils like the bones of the tongue apparatus, tendons for wing and leg muscles, and even the remnants of its last meal of a small mammal.

"It is the amazing preservation of the bones of the eye in this fossil skull that allows us to see that this owl preferred the day and not the night," said Li, the paper's first author.

Nocturnal animals require overall larger eyes and bigger pupils to see in low-light conditions, but diurnal animals have smaller eyes and pupils.

The researchers rebuilt the size and shape of the ring around the iris and pupil of the fossil's eye in order to determine the overall diameter of the ring and the opening for light in the middle.

Thereafter, they compared it with the eyes of 55 species of reptiles and more than 360 species of birds including many owls, reaching a conclusion that it most resembles the eyes of living owls which is largely not nocturnal.

Using the avian family tree to reconstruct the ancestral habits of birds, including owls, they found that this group of owls was diurnal although the ancestor of all living owls was almost certainly nocturnal, according to the study.

"This fossil skeleton turns what we thought we knew about the evolution of owls on its head," Li said. (Xinhua)