First fossil of a daytime active owl found at the edge of the Tibetan Plateau
Fossil skeleton of the daytime active owl Miosurnia diurna from China (below) with an expanded view of the skull (top left). The eye bones or scleral ossicles are false colored blue and set in comparison with an intact ring in the skull of a pygmy owl Glaucidium (top right). Credit: IVPP

The well-preserved fossil skeleton of an extinct owl that lived more than six million years ago has been discovered by a research team. The owl was active in the daytime, not at night, according to their study.

The findings of the team were published in the PNAS.

The Linxia Basin of China's Gansu province, at the edge of the Tibetan Plateau, contains rocks deposited during the late Miocene Epoch at an elevation greater than 2,100 meters.

The entire skeleton is preserved 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.

The first record of an ancient owl being active during the day is from this extinct species. The researchers named the species after its close living relative, the Northern Hawk Owl. The features of the skull and skeleton, including a large bump on part of the cheekbone just behind the eye, show that Miosurnia is a part of the global owl group. The night millions of years ago was rejected by the Surniini, which included the Northern Hawk Owl.

Owls are the only birds that are mostly nocturnal. Many people don't realize that a few owls are mostly nocturnal.

The preservation of the bones of the eye in the owl's skull allows us to see that the owl preferred the day and not the night.

First fossil of a daytime active owl found at the edge of the Tibetan Plateau
Reconstruction of the extinct owl Miosurnia diurna perched in a tree with its last meal of a small rodent, overlooking extinct three-toed horses and rhinos with the rising Tibetan Plateau on the horizon. Credit: IVPP

Small bones called scleral ossicles form a ring around the eye's iris and pupils. In low-light conditions, nocturnal animals need bigger eyes and bigger pupils, while diurnal animals have smaller eyes and pupils.

The small scleral ossicles collapsed into the owl's eye sockets because of the decay of the soft parts of the eye. To rebuild the ring around the eye, the paleontologists had to measure the individual small bones and do some basic geometry.

It was a bit like playing with Lego blocks, just digitally, according to the doctor. The scientists were able to determine the diameter of the ring and the opening for light in the middle by putting them back together correctly.

The IVPP scientists compared the eyes of 55 species of reptile and more than 350 species of birds, including many owls. The size and shape of the fossil's eye and its relatively small opening for light made the scientists conclude that it most resembles the eyes of living owls.

The scientists used behavioral data from over a hundred species of birds to conduct an ancestral state reconstruction. The researchers used the family tree of birds to determine which birds were nocturnal or diurnal.

The results show that the ancestors of all owls were nocturnal, but the ancestors of the Surniini group were diurnal. When the scientists added the fossil to the analysis, the probability of the ancestors being diurnal increased to 100%. The evolution of diurnal behavior in this owl group can be seen in both lines of evidence.

The evolution of owls on their head is turned on its head by the fossil skeleton.

The first record of an evolutionary process lasting millions of years and stretching across the globe is the owl's ability to "reject the night for some fun in the sun."

More information: Early evolution of diurnal habits in owls (Aves, Strigiformes) documented by a new and exquisitely preserved Miocene owl fossil from China, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2119217119 Journal information: Proceedings of the National Academy of Sciences Citation: First fossil of a daytime active owl found at the edge of the Tibetan Plateau (2022, March 28) retrieved 28 March 2022 from This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.