The palaeontology collection at Tāmaki Paenga Hira Auckland War Memorial Museum is home to approximately 23,000 fossil specimens from Aotearoa and abroad. This includes the bones of ancient sea monsters, ammonites the size of tractor tires, and tiny foraminifera no bigger than a grain of sand. Most of these fossils are stored off display, unseen to everyday visitors to the museum. However, the Improved Documentation Enhanced Access (IDEA) project aims to change this. Over the course of the recently completed project, 2,224 paleontology records were uploaded to Collections Online and a number of interesting and important specimens were photographed for the first time, opening up our fossil collection for the world to see. 

Many fossil molluscs (clams and snails) with unique back stories or interesting features were catalogued throughout the duration of the IDEA palaeontology project, emphisising the wealth and variability of specimens present in the museum’s collection. Tropical cone snails, which are no longer found living in Aotearoa but occur in rocks throughout the country, hearken back to an age when sea-surface temperatures were much warmer than they are now. Meanwhile, specimens collected from the former Inner Napier Harbour prior to its uplift above sea-level during the 1931 earthquake attest to the active and ever changing nature of our landscape. Perhaps the most interesting specimens though are fossil shells that fluoresce under ultraviolet (UV) light, glowing with bright and striking colours that are normally invisible to our human eyes. This works similarly to the blacklight lamps used in glow-in-the-dark minigolf and nightclubs, which emit a form of UV light that causes brightly coloured clothing to glow in dazzling neon shades.  

Fossil shells may fluoresce in several different ways. Most commonly, they do so as a result of remineralisation, where the original shell material is replaced during the fossilisation process by fluorescent minerals — such as calcite. Much rarer and far more intriguing is the fluorescence of formerly pigmented, or coloured areas of a shell under UV light so that the animal’s original patterning is spectacularly revealed. Most of the fossil shells in the Museum’s collection appear bleached and colourless, with their once vibrant colours having long faded over time. Some show very faint evidence of patterning in natural light. However only a select few possess patterns that glow under UV. Why might this be? Well, scientists are still trying to understand how pigmentation works in molluscs, and as a result aren’t completely sure why only some fossil shells display these fluorescent patterns. It is possible that this may be due to oxidising chemical reactions, as in some cases fluorescence is only observed on parts of a shell that have been exposed at length to direct sunlight. Experiments recreating these oxidising reactions have had variable success, and studies into this phenomenon continue. 

Because fossils don’t usually contain evidence of colouration, the pretty fluorescent patterns that adorn these shells are extremely useful to the paleontologists who study them. Usually, the classification and description of fossils is based on their form and shape alone, so the addition of patterning on some shells can be a handy way to further characterise extinct species, and compare them to their living relatives. For example, the group of sea snails known as volutes are adorned by a huge range of patterns, including zig-zags, stripes, spots, and blotches, that can be used to tell different species apart. The fluorescent markings on the volute specimen figured here identify it as Scaphella floridana — a two to three million year old species related to the modern and highly prized Junonia shell from the southern United States. Patterns can also be used as indicators of an animal's behaviour and lifestyle. Bold and brightly coloured patterns are often an indication of danger, and are sometimes used by poisonous animals as a warning to predators to stay away. On the other hand, earthy tones and mottled patterns in other creatures are used as a form of camouflage to help them blend into their surroundings and avoid becoming something else’s lunch! The fossil shells of carnivorous tropical gastropods, including volute and cone snails, are often intricately patterned and are among the most interesting to view under UV lighting.  

While fluorescing shells have been reported from fossil deposits throughout the world, all those with fluorescent patterning in Auckland Museum’s palaenotology collection were originally found in the same two to three million year old, Pliocene-aged sediments in Florida, United States. Along with many of our other fossils, these originally came from the personal collections of Arthur William Baden Powell, Charles Reed Laws, and Harold John Finlay, who were three of Aotearoa New Zealand’s leading palaeontologists during the 20th Century. Specimens from around the world were obtained by Powell, Laws and Finlay through a combination of collection trips and trades with other collectors, and have contributed to paleontological research and our understanding of Aotearoa’s ancient history. Their collections were subsequently acquired by Tāmaki Paenga Hira Auckland War Memorial Museum in the early 20th Century, and now these fascinating and important fossils are accessible for everyone to see via the Collections Online portal.  

FURTHER READING ON FLUORESCENT PIGMENTATION IN FOSSIL SHELLS: 

Hendricks, J. R. (2015). Glowing seashells: diversity of fossilized coloration patterns on coral reef-associated cone snail (Gastropoda: Conidae) shells from the Neogene of the Dominican Republic. PLoS One, 10(4). 

Wilson, E. C. (1975). Light show from beyond the grave. Terra (the Members Magazine of the Natural History Museum Alliance of Los Angeles County), 13, p. 10-13.