Fish eye sheds light on color vision

A fish eye from a primitive time when Earth was but one single continent, has yielded evidence of color vision dating back at least 300 million years, researchers said on December 23, 2014.

Analyzing the fossilized remains of a fish from the spiny shark family that lived long before the dinosaurs, scientists discovered light-sensing rod and cone eye cellsthe oldest ever found.

This is the first discovery of vertebrate retinal fossils, said Gengo Tanaka from Japans Kumamoto University, who co-authored the study in the journal Nature Communications.

It is rare for palaeontologists to find eye remains, as the soft tissue generally decays within 64 days, the authors of the study said.

However, the Hamilton Quarry in Kansas is a treasure trove of unusually well-preserved fossilsan entire ecosystem having been rapidly buried under sediment.

They included the extinct fish Acanthodes bridgeiamong the oldest known vertebrates with jaws.

It had a long, streamlined body and fins with spines, is believed to have lived in shallow, brackish water, and died out at the end of the Permian period about 250 million years ago when nearly 90 percent of species disappeared in the largest extinction in Earths history.

An A. bridgei specimen found at the quarry retained elements of the original eye color and shape, and a light-absorbing pigment in the retina.

The remains had been preserved under a thin coating of phosphate, Tanaka told AFP.

Analysis of the tissue provides the first record of mineralized rods and cones in a fossil, said the study.

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Fish eye sheds light on color vision