Poschmann et al. also described a second species as Diploaspis muelleri. A third species, Diploaspis praecursor (Late Silurian, Bertie Group, New York State)
Paul A. Selden, Lamsdell and Liu Qi, expanded to include the species Diploaspis praecursor, described in 2017. It showcases the phylogenetic relationships
America (Silurian, Bertie Group, New York State) is the oldest species of Diploaspis". Geological Magazine. 154 (1): 175–180. Bibcode:2017GeoM..154..175L.