Papiliomaris

Papiliomaris (IPA: [paːˈpɪ.li.oːˌma.rɪs]) (meaning "butterfly of the sea" or "sea butterfly") is a genus of bivalved (referring to the carapace) euarthropod with uncertain placement from the Silurian Waukesha Biota in Wisconsin, USA. The type and only species is Papiliomaris kluessendorfae, known from various specimens typically comprising part and counterpart fossils of the whole animal. Before this taxon was formally described, the fossils now attributed to it were referred to as the butterfly animal in the literature and informal discussions.

The specimens that are now Papiliomaris were once the subject of heavy taxonomic debate due to their unique morphology, however, a team of researchers in 2025 assigned these fossils to the species P. kluessendorfae with euarthropod placement. Even still, its exact placement within the phylum is still not fully understood, much like other contemporary euarthropods from the Waukesha Lagerstätte.