The discovery of an exceptionally preserved fossil skeleton of a long-extinct owl in the Tibetan Plateau reveals that this species hunted throughout the day, signalling a significant shift in our understanding of owl evolution.
Digital Desk: The fossil of the 6 million-year-old ‘Day Owl’ was preserved well and unearthed in China. The owl species is named Miosurnia diurna owl, which lived in the late Miocene Epoch.
According to the provided reports, the fossil was discovered at the border of the Tibetan Plateau, approximately 7,000 feet (2,100 metres) up in China’s Gansu province’s Linxia Basin.
Researchers from the Chinese Academy of Sciences conducted a detailed investigation of the skeleton’s fossilised eye bones, which revealed that this species was active during the day rather than at night, unlike most modern owls.
The fossil includes almost the entire skeleton, from the tip of the skull to the tail bone and body components rarely found as fossils.
The hyoid bones of the tongue apparatus, the airway, the kneecap, tendons for wing and leg muscles, and even the remains of a small mammal’s last meal are among these.
‘The incredible preservation of the eye bones in this fossil skull shows that this owl favoured the day over the night,’ said Dr Li, the study’s first author.
The species was named Miosurnia diurna after a near living relative, the diurnal Northern Hawk Owl (Surnia ulula).
Miosurnia belongs to the Surniini owl family, based on its skull and skeleton traits, which include a prominent protrusion on the cheekbone right below the eye.
According to their findings, the Surniini, including Miosurnia, the Northern Hawk Owl, and pygmy owls, rejected the nighttime millions of years ago.
It is the first time an ancient owl has been discovered as ‘diurnal,’ or active throughout the day.
Scleral ossicles are tiny bones in the outer area of the eye that form a ring around the pupil and iris.
Nocturnal animals need more enormous eyes and pupils to see in low-light circumstances, whereas diurnal species need smaller eyes and pupils.
The soft components of the eye of the Miosurnia diurna fossil had long since disintegrated, leaving the tiny trapezoidal scleral ossicles collapsed into the owl’s eye socket.
To recreate the size and shape of the ring around the eye, palaeontologists had to measure each tiny bone and perform some basic geometry.
Dr Stidham described how the 16 small identical bones overlap to form a ring around the iris and pupil as “a bit like playing with Lego pieces, but digitally.”
The scientists were able to estimate the overall circumference of the ring and the aperture for light in the middle by putting them back together correctly, he said.
The IVPP scientists next compared the scleral ossicles of the fossil owl to the eyes of 55 reptile species and more than 360 bird species, including several owls.
The scientists discovered that the size and form of the fossil’s eye and its smaller soft opening most closely mimic the eyes of contemporary Surniini owls.
They also looked at behavioural data from over 360 species of birds to see which ones were most likely nocturnal or diurnal.
Their findings demonstrate that whereas all extant owls’ ancestor was almost probably nocturnal, the Surniini group’s ancestor was diurnal.
‘What we thought we knew about the evolution of owls is turned on its head by this ancient skeleton,’ stated Dr Li.
Miosurnia diurnia is the first record of an evolutionary process spanning millions of years and across the globe in which owls evolved to reject the night for some fun in the sun,’ according to Dr Stidham.