Marine molluscs are exceptional in Cretaceous ambers. Palaeoellobium decampsi gen. nov., sp. nov. is the first gastropod ever preserved in French uppermost Albian-lowermost Cenomanian opaque amber. It belongs to the Ellobiidae that are distributed in the Cenozoic supralittoral zones in close vicinity of the mangroves. It has been discovered by non-destructive X-ray phase-contrast imaging. The forest of conifers that produced the amber embedding this gastropod did not form its habitat, and it may have been transported to the foreshore detritus. Palaeoellobium decampsi contributes to the understanding of the ellobiid early adaptive radiation known by few taxa, compared with the significant Cenozoic diversification.
