Ancient seashells in museum collection tend to look drab white, but high tech equipment reveals many ancient shells displayed distinctive patterns and colors.
Given the uniqueness of their appearance, some of the shells were determined to belong to newly documented species of cone snails, which are predatory mollusks. They are described in the current issue of the journal PLOS ONE.
"This study allows comparisons to be made between cone snail diversity patterns on modern and fossil coral reef systems for the first time," wrote the study's author Jonathan Hendricks, a geologist at San Jose State University.
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Hendricks cleverly placed the drab-looking old shells under ultraviolet light. In doing so, the organic matter remaining in the shells, which date to 6.6–4.8 million years ago, became visible. It revealed the original coloration patterns of the shells that encased the large marine snails.
Using this technique, Hendricks was able to view and document the coloration patterns of 28 different cone shells, 13 of which are now suspected to be new species. One of the most striking examples was a polka-dotted shell. This unmistakable pattern is thought to be extinct among modern cone snails.
The 13 new species are as follows (question marks added by Hendricks to indicate ongoing research on the species' phylogeny): Profundiconus? hennigi, Conasprella (Ximeniconus) ageri, Conus anningae, Conus lyelli, Conus (Atlanticonus?) franklinae, Conus (Stephanoconus) gouldi, Conus (Stephanoconus) bellacoensis, Conus (Ductoconus) cashi, Conus (Dauciconus) garrisoni, Conus (Dauciconus?) zambaensis, Conus (Spuriconus?) kaesleri, Conus (Spuriconus?) lombardii, and Conus (Lautoconus?) carlottae.
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All of the mollusks hailed from the northern Dominican Republic. While some, like the polka dot one, went extinct, others continued to slowly evolve over the years. Some shell colors and patterns have even remained relatively unchanged over this lengthy period of time.
Hendricks determined that each of the three studied coral reef deposits (where the shells came from) contained a minimum of 14–16 cone snail species. These are, he wrote, "levels of diversity that are similar to modern Indo-Pacific reef systems."
There's still a mystery concerning the prehistoric shells, though.
Hendricks explained, "While the use of UV light to reveal ancient shell coloration patterns has proved to be a useful technique for understanding the systematics of some fossil mollusks, we still do not have a clear understanding of exactly what compounds are responsible for pigmentation in modern shells, much less what matter is actually fluorescing in the fossil shells."
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It will be interesting to see if those compounds can be identified soon. In addition to telling us more about what ancient seashells looked like, perhaps similar compounds added color and patterns to other early animals. Research over the past few years on non-avian dinosaurs, for example, found that, like modern birds, they sported all sorts of eye-catching colors and patterns.
One thing is clear: life before Homo sapiens was definitely not just drab black and white. It was full of vivid hues, from the feathers of the earliest birds to the seashells found on sand, rocks and coral reefs.
Image: Three of the newly described species, Conus carlottae (left column), Conus garrisoni (middle column), and Conus bellacoensis (right column) photographed under regular light (top row) and ultraviolet light (middle row). The brightly fluorescing regions revealed under ultraviolet light would have been darkly pigmented in life (bottom row), Credit: Jonathan Hendricks