Modern cone snail shells are washed in color and full of intricate patterns. These aren't just pleasing to the eye; they also help scientists tell different species apart. But after millions of years in the sea and sand, the remnants of ancient cone snails aren't quite so colorful.

Luckily, scientists can use ultraviolet light to draw out the color patterns of these ancient shells. Areas that were once pigmented shine under UV light. By taking these UV photos and inverting them (so the parts that glow become dark), researchers can create images like the ones above that reveal a shell's long-lost pattern.

In a new study published Wednesday in PLOS ONE, San Jose State University associate professor Jonathan Hendricks used the technique on 28 different species of cone snail found in the Dominican Republic ranging from 4.8 million to 6.6 million years old.

By drawing out the patterns of the fossils, he was able to classify them by species. In many cases he found their patterns to be quite similar to surviving species. But in other cases -- like the proposed new species Conus carlottae -- patterns were strikingly unfamiliar. This species had large polka dots all over its shells, which isn't a pattern seen in cone snails today.

All in all, Hendricks's paper proposes 13 new species and places most of these (and the more familiar shells) into known family groupings of cone snails. Because cone snail fossils are usually white-washed and fairly similar in shape, such classification would be all but impossible without the color-trickery of ultraviolet light. Researchers aren't sure what compounds in shells make this fluorescence occur long after true color has faded, but it's a valuable -- and beautiful -- geological tool.

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