| 1 | Some blades of compound chaetae with proximal tooth curved, almost connecting with blade edge. Pharyngeal tooth on anterior 1/3 of pharynx | 2 |
| – | Proximal tooth not so curved. Pharyngeal tooth about half way along pharynx | Opisthodonta morena Langerhans, 1879 (1) |
| 2 | Blades of compound chaetae on mid body and posterior segments with distal tooth somewhat smaller than subdistal one | Opisthodonta serratisetosa López, San Martín & Jiménez, 1997 (1) |
| – | Distal tooth on blades minute or absent | Opisthodonta longocirrata (Saint-Joseph, 1886) (1, 13) |
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