Scientists have discovered a fossilized fish eye so well preserved its insides are still visible under a scanning electron microscope.

The scan reveals eye cells that have existed for at least 300 million years and that have seen the colors of the prehistoric world. It's also the very first time that fossilized photoreceptors from a vertebrate eye have ever been found.

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The cells that line the retina of our eyes are called rods and cones. Rods are long and thin, and more sensitive to light than cones. Cones, which are triangular, allow us to see in color.

Rods are responsible for peripheral and night vision. Cones help perceive fine detail and rapid changes. Both these cells rely on pigments to absorb light.

Using chemical analysis, scientists found evidence of one of these pigments, melanin, in the fossilized eye, as well.

The 300 million year-old fish fossil with its eye tissue is probably one of the earliest known creatures with a backbone.

Scientists examined the fossil specimen of a fish called Acanthodes bridgei. They discovered the fish in Kansas and kept it at the National Museum of Nature and Science in Tokyo.

The fish is about four inches longs and is the last known common ancestor of modern jawed fish like barracudas and sharks.

Scientists also discovered granules the size and shape of particles found in modern fish eyes. These granules are made of eumelanin, a pigment that absorbs light and helps animals see.

Gengo Tanaka of Kumamoto University in Japan, the lead author of the paper, said that studying this fish species can help in reconstructing the colors of extinct animals.

TagsFossilized Fish Eye, Ancient fish, Fossil, animal fossil, Acanthodes bridgei, modern jawed fish, barracudas, sharks, animal extinction, eyes retina