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Hi all, Some time ago I found this shell in (what I believe to be) the French Upper Muschelkalk (Triassic). Now I'm not into shells myself, but to judge from the remains of operculum on the underside of it, the specimen concerns an oyster. Most strikingly, however, the shell has a pattern of darker-coloured lines that do not correspond to any three-dimensional/elevational differences on the shell surface - which is, in fact, entirely flat. I haven't seen this on a fossil shell before. Now when doing a Google search for my response on whether it would be possible for crustacean carapaces to retain traces of their original colour, I bumped into an article that described that molluscs may incorporate melanin in the calcite of their shells to create the colour patterns we see (e.g., here). This got me wondering: could the lines I'm seeing indeed be traces of the original melanin pigmentation of this shell? And, if so, how common is this phenomenon? Does anybody else have examples of such shells? I'd also be very happy if someone could furnish me with a genus or species name to go with my specimen. But here I'd like to primarily raise the topic of ancient colour reconstruction in shells.