According to a team of paleontologists from the United Kingdom and Japan led by Dr Haruyoshi Maeda of Kyushu University Museum, color vision evolved in animals as early as 300 million years ago (Carboniferous period).
Carboniferous fish Acanthodes bridgei. Image credit: Gengo Tanaka et al.
Dr Maeda and his colleagues studied the tissues in the fossilized eye of a 300-million-year-old fish, named Acanthodes bridgei.
The specimen – an extinct species of fish that resembles a small shark – was uncovered from the Upper Carboniferous Hamilton Formation in Kansas, the United States.
It was scanned under an electron microscope and further chemical analysis on the fossil showed evidence of cone cells and rods in the retina.
“This fossil fish eye is the first evidence to suggest animals saw in color as early as 300 million years ago,” said Prof Andrew Parker of the Natural History Museum in London, who is a co-author of the paper published in the journal Nature Communications.
Parts of the visual system are not usually preserved in the fossil record because the soft tissue of the eye and brain decay rapidly after death.
“It is the first case of color vision in an ancient, extinct animal, proving color vision existed a long time before the Jurassic period,” Prof Parker said.
The retina of Acanthodes bridgei is very well preserved, enabling paleontologists to find the first record of cone cells and rods in animals.
Prof Parker added: “these are both in the retina of a modern human and animal eye to enable color vision.”
“We can now use these techniques to examine color pigments in other ancient animals, bringing us closer to the time when color vision first evolved.”
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Gengo Tanaka et al. 2014. Mineralized rods and cones suggest colour vision in a 300 Myr-old fossil fish. Nature Communications 5, article number: 5920; doi: 10.1038/ncomms6920
