Sea stars and some other echinoderms might have had complex visual systems for roughly the past 80 million years.
Some existing echinoderms, such as brittle stars, are covered in crystal calcite microlenses that are sensitive to light. To determine the evolutionary history of these structures, Przemysław Gorzelak at the Polish Academy of Sciences in Warsaw and his team analysed 75-million-year-old brittle-star and starfish fossils using a scanning electron microscope. Both kinds of fossil contained structures (pictured) that matched modern echinoderms' microlenses in size and shape.
After an explosion in the diversity of fish and crustacean predators began around 80 million years ago, echinoderms may have developed visual systems to avoid such predators, the researchers say.