China had owls that were active during the day. Study reveals first fossils of extinct species

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New Delhi: An international team of researchers has discovered the incredibly well-preserved fossil skeleton of an extinct owl that lived over six million years ago in China. The owl was active during the day, not at night, as the skeleton’s fossilized eye bones indicate.

The study, conducted by researchers from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences, was recently published in the journal Proceedings of the National Academy of Sciences (PNAS).

Where was the fossil found?

Scientists discovered the fossil skeletons between rocks deposited at the end of the Miocene, at an altitude of more than 2,100 meters, in the Linxia Basin of China’s Gansu Province, located on the edge of the Tibetan Plateau.

How well is the fossil preserved?

According to the study, almost the entire skeleton, from the tip of the skull through the wings and legs to the tailbone, is preserved in the fossil. He also preserved body parts rarely seen in fossils. These include the bones of the tongue apparatus called the hyoid, the trachea, the patella, the tendons of the wing and leg muscles, and even the remains of a small mammal’s owl’s last meal.

First record of an ancient owl being diurnal

According to the study, this extinct species is the earliest record of an ancient diurnal or daytime-active owl. The Diurnal Northern Hawk Owl (Surnia ulula) is a close living relative of the owl species whose fossil was discovered. Therefore, the extinct species was named Miosurnia diurna in reference to its close living relative.

Researchers inferred that Miosurnia is part of the global Surniini owl group by studying skull and skeletal features, including a large bump on part of the cheekbone just behind the eye. Miosurnia is the extinct genus of the Late Miocene Surniini group. Miosurnia diurna is the only species belonging to the genus.

The results show that the Surniini, which include Miosurnia, the Northern Hawk Owl and the Pygmy Owls, rejected at night millions of years ago, according to the study.

Owls are essentially nocturnal animals. However, a few species are in fact largely diurnal.

How did researchers determine that the owl is diurnal?

Dr Li Zhiheng, the first author of the study, said in a statement published by the Chinese Academy of Sciences that it is the amazing preservation of the eye bones in this fossil skull that allows researchers to see that this owl preferred the day and not the night.

The small bones that form a ring around the pupil and the iris in the other region of the eye are called scleral bones. To see in low light conditions, nocturnal animals need overall larger eyes and larger pupils. However, diurnal animals have smaller eyes and pupils.

The soft parts of the eye of the Miosurnia diurna fossil had decayed a long time ago, according to the study. As a result, the small trapezoidal scleral ossicles were left randomly collapsed in the owl’s orbit.

It’s for this reason that paleontologists had to measure the small individual bones and do some basic geometry to reconstruct the size and shape of the ring around the eye, according to the study.

Dr Thomas Stidham said it was a bit like “playing with Lego blocks, just digitally”. He described how the 16 similar small bones overlap to form a ring around the iris and pupil.

The researchers compared the scleral ossicles of the fossil owl with the eyes of 55 species of reptiles and more than 360 species of birds, including many owls.

Scientists observed the size and shape of the fossil’s eyes and found that it had a relatively smaller opening for light. Based on these factors, they determined that the eyes of the extinct owl most closely resemble the eyes of living owls of the Surniini group, which is largely non-nocturnal.

Using behavioral data from more than 360 species of a diversity of birds, the researchers performed an ancestral state reconstruction, in which they used the avian family tree to reconstruct the ancestral habits of the birds. birds, including owls. They did this to determine which owls were likely nocturnal or diurnal.

The study authors found that the ancestor of all living owls was almost certainly nocturnal. However, the ancestor of the Surniini group was diurnal.

The scientists also added the Miosurnia diurna fossil in the statistical analysis. By doing so, the probability that Surniini’s ancestor was diurnal increased to 100%. Therefore, the behavioral and eye findings point to the evolution of diurnal behavior in the group of Surniini owls.

According to the statement, Dr Stidham said Miosurnia diurna is the earliest record of an evolutionary process spanning millions of years. He said owls evolved to “throw off the night for fun in the sun”.

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