Rhadinichthys plumosum was named by Elliott (2018) [Dubious generic placement]. Its type specimen is GLAHM 152845, a skeleton (slab of shale containing disarticulated specimen), and it is a compression fossil. Its type locality is Ardenrigg Colliery, pit number 6, Wester Bracco, which is in a Westphalian A fluvial-deltaic shale/coal in the Scottish Lower Coal Measures Formation of the United Kingdom.