<==o †Protopteraspidae Novitskaya, 1983
   |--o †Canadapteraspis
   |  |-- †C. thymostomata
   |  `-- †C. alocostomata Dineley & Loeffler, 1976
   |--o †Protopteraspis Leriche, 1924 [Simopteraspis White, 1950]
   |  |?- †P.? arctica Elliott & Dineley, 1983
   |  |?- †P.? corniga Elliott & Dineley, 1983
   |  |-- †P. aquilonia Blieck, 1981
   |  |-- †P. pygmaea Elliott & Dineley, 1983
   |  |-- †P. sartokia Elliott & Dineley, 1983
   |  |-- †P. siliktokia Elliott & Dineley, 1983
   |  |-- †P. micra Ilyès et al., 1995
   |  |-- †P. primaeva (Kiaer, 1928) [Simopteraspis primaeva]
   |  |-- †P. gosseleti (Leriche, 1906) [incl. P. leathensis White, 1935] [Pteraspis gosseleti Leriche, 1906; Pteraspis (Protopteraspis) gosseleti (Leriche, 1906) Leriche, 1924; Simopteraspis gosseleti (Leriche, 1906)]
   |  |-- †P. vogti (Kiaer, 1928) [Simopteraspis vogti]
   |  `-- †P. whitei (Denison, 1955)
   `-- †Trygonaspis

Reference(s):