292-13 Spectacular North Carolina Mollusk UV Color Patterns / Implications

Session: Life and Environments Through Time and Space: Multi-Record Approaches to Stratigraphic Paleobiology, Part II

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It is well established that original color patterns can be revealed using black light on a wide variety of fossil mollusks.  Data of this kind on the US eastern seaboard appears sparse.  Here we examine over 80 genera / 100 species of gastropod and bivalve that display a wide variety of spectacular UV patterns. Some of these patterns are backed up by faint visible color traces.  Over 4,000 specimens that fluoresce naturally from sun exposure were used.  No additional preparation was necessary.  They originate from two different North Carolina locations: Old Dock, (Lower Waccamaw Formation ~2 Ma) and Fountain, (Yorktown Formation ~4 Ma).   

We examine these two sites as they relate to each other (by species and color pattern); and as they relate to nearby North Carolina beaches with their modern extant inhabitants.  In the case of Old Dock, Holden Beach is less than 30 miles away, indicating many of the shells found there today are the direct descendants of the specimens being examined.

The results are fascinating – we find color patterns remaining the same, morphing over time or disappearing altogether.  We find species changing dominance, evolving, moving or going extinct.  Example: At Fountain (4Ma), Glycymeris americana is the underdog species with Tucetona subovata being the dominant large Glycymerid.   Glycymeris americana had a single color pattern at Fountain.  By 2 million years later at Old Dock, the large Tucetona was gone and Glycymeris americaca was dominant and now had 3 different color patterns, the Fountain pattern being recessive, a hybrid pattern being dominant and the modern extant pattern just beginning to be seen.  Fast forward another 2 million years and the Fountain & hybrid patterns are completely gone and only the extant pattern remains.

Based on similar analyses, some previous classifications and identifications are confirmed, while others are called into question.  Example: Existing literature lists 26 different Prunum species at Old Dock – but black light reveals only 4 different color patterns. 

UV fossil color patterns can be an exciting new tool in helping improve our understanding of both fossil and extant classifications.  Having now refined a method for coaxing out latent color patterns using just the sun, we anticipate that many more patterns will be discovered soon.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8526

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