In fossils from the Mesozoic Era, traces of colour patterns are very rarely observed. However, the investigation with UV light of scallops from the Triassic period -- right from the beginning of the Mesozoic Era -- shows that colour patterns are preserved much more frequently than previously thought. UV light, which is invisible to the human eye, excites organic compounds in the fossils causing them to glow. This reveals a surprising variety of colour patterns: different variations of stripes, zigzags and flame patterns. The diversity of colour patterns is similar to those of today's seashells found on a beach.

However, the colour patterns of today's scallops do not show any fluorescence. "In the case of the Triassic shells, fluorescent compounds were only formed in the course of fossilisation through oxidation of the original pigments," explains Dr Klaus Wolkenstein from the Geosciences Centre at the University of Göttingen, who is currently carrying out research at the University of Bonn. Surprisingly, the fossil shells show different fluorescent colours, depending on the region where they were found. "The colour spectrum ranges from yellow to red with all the transitions in between, which suggests that there were clear regional differences in the fossilisation of these scallops," adds Wolkenstein.