Order
Thecideida Elliott, 1958
Klassificering
| Organism group | Biota |
| Domain | Eukaryota |
| Kingdom | Animalia |
| Phylum | Brachiopoda |
| Subphylum | Rhynchonelliformea |
| Class | Rhynchonellata |
| Order | Athyridida |
| Atrypida | |
| Orthida | |
| Pentamerida | |
| Protorthida | |
| Rhynchonellida | |
| Spiriferida | |
| Spiriferinida | |
| Terebratulida | |
| Thecideida |