After Kazlev, 2000, and “Wikipedia”, 2012
<==o †Chasmataspidida Caster & Brooks, 1956 [Diploaspidida Simonetta & Delle Cave, 1978]
|?- †“Eurypterus” stoermeri Novojilov, 1959
|--o †Chasmataspidae Caster & Brooks, 1956
| `-- †Chasmataspis laurencii Caster & Brooks, 1956; Ord. NAm.
`--o †Diploaspididae Størmer, 1972 [Heteroaspididae Størmer, 1972]
|-- †Achanarraspis reedi Anderson, Dunlop & Trewin, 2000; Dev. WEu.
|--o †Diploaspis Størmer, 1972 [Heteroaspis Størmer, 1972] Dev. CEu.
| |-- †D. casteri Størmer, 1972 [Heteroaspis novojilovi Størmer, 1972]
| `-- †D. muelleri Poschmann, Anderson & Dunlop, 2005
|-- †Forfarella mitchelli Dunlop, Anderson & Braddy, 19994; Dev. WEu.
|-- †Loganamaraspis dunlopi Tetlie & Braddy, 2004; Dev. WEu.
`-- †Octoberaspis ushakovi Dunlop, 2002; Dev. NEEu.
Reference(s):