When the first thorough examination of Opabinia in 1975 revealed its unusual features, it was thought to be unrelated to any known phylum,[1] or perhaps a relative of arthropod and annelid ancestors.[2] However, later studies since late 1990s consistently support its affinity as a member of basal arthropods, alongside the closely-related radiodonts (Anomalocaris and relatives) and gilled lobopodians (Kerygmachela and Pambdelurion).[3][6][5][6][1][9][10]