<==o AZYGIIDA n. n.
|--o AZYGIATA
| `--o AZYGIOIDEA*
| |-- Azygiidae
| |-- Bivesiculidae
| `-- Aphanhysteridae
`--o HEMIURATA
|--o HEMIUROIDEA
| |-- Hemiuridae
| |-- Halipegidae
| |-- Bathycotylidae
| |-- Botulidae
| |-- Ptychogonimidae
| |-- Hirudinellidae
| |-- Sclerodistomatidae
| |-- Mabiaramidae
| |-- Prosogonotrematidae
| |-- Oesophagicolidae
| |-- Arnolidae
| |-- Lampritrematidae
| |-- Lobatovitelliovariidae
| `-- Syncoeliidae
|--o ISOPARORCHIOIDEA
| |-- Isoparorchiidae
| |-- Albulatrematidae
| |-- Aerobiotrematidae
| |-- Tetrasteridae
| |-- Dictysarcidae
| |-- Pelorohelminthidae
| `-- Cylindrorchiidae
|--o ACCACOELIOIDEA
| `-- Accacoeliidae*
`--o DIDYMOZOOIDEA
`-- Didymozoidae*
Reference(s):
Parker, S. P. (ed.), 1982: Synopsis and classification of living organisms. Vols. 1 & 2
–McGrew-Hill Book Company