Before scientists believed that the third eyes are “a characteristic feature of the larval stage of animals” that lived in the Paleozoic era (541 – 252 million years ago). However, the new, well-preserved fossils show a different picture – a middle eye located in the middle of the forehead.

what is known

When the researchers examined a specimen of Aulacopleura koninckii that was missing part of its head, they saw “small oval spots of equal size, dark, inconspicuous, on the front of the head.”

The clear, ordered appearance distinguishes this structure from accidental formations from decay or fossilization and corresponds to the expected remains of simple median eyes equipped with a layer of pigment. Even if this is a single find, it supports the idea that trilobites originally had middle eyes.
– Lead author of the study, Brigitte Schenemann, a professor at the Institute of Zoology at the University of Cologne in Germany, said in a statement.

At various stages of their evolution, trilobites likely had one to several median eyes. For example, the researchers found that the trilobite Cyclopyge sbilla had three middle eyes equipped with human-like lenses, while Cindarella eucalla had four. Today, most modern insects and crustaceans have three median eyes.

5 interesting facts about trilobites

• Trilobites lived on Earth for about 300 million years, from the early Cambrian period to the end of the Permian period.
• They are known for their characteristic segmented bodies covered with a hard calcium carbonate exoskeleton. Some species had spines or horns on their exoskeletons for protection.
• Trilobites ranged in size from 1 millimeter to as short as 70 centimeters. The largest trilobite ever found, Isotelus rex, was found in Manitoba, Canada, and was over 70 centimeters long.
• In some species, the eyes were located on the legs, which allowed them to see in different directions.
• Trilobites are one of the most diverse groups of animals in the fossil record, with over 20,000 different species. They lived in a variety of marine environments, including shallow waters, reefs, and deep oceans, and their fossils can be found on every continent.