| 1. | Mature spikes mostly with 4 or more joints | 2 |
| Mature spikes with 1-3 joints | 5 | |
| 2. | Spikes more than 2 mm thick | 3 |
| Spikes less than 2 mm thick | 4 | |
| 3. | Spikes not constricted at nodes | T. major (NT WA QLD) |
| Spikes constricted at nodes | T. monilifera (NT QLD) | |
| 4. | Spikes of one type only | T. pubescens (NT WA QLD) T. constricta |
| Spikes of two different types | T. x heteromorpha (QLD) T. pubescens x T. major |
|
| 5. | Spikes constricted at the nodes, usually 3 jointed | T. sp . (Morehead R., Clarkson 8086) (QLD) |
| Spikes not constricted at the nodes, usually less than 3 jointed | 6 | |
| 6. | Spikes 11-20 mm long, 2-3 (rarely 1) jointed | T. striata (NT) |
| Spikes 3-9 mm long, 1 (rarely 2) jointed | 7 | |
| 7. | Culm with 6-9 nodes; lower glume smooth or slightly rugulose | 8 |
| Culm with 10-15 nodes; lower glume not smooth | 9 | |
| 8. | Joints 2.5-3 mm long; lower glume concave inside view | T. rariflora (QLD) |
| Joints 3-6 mm long; lower glume ±straight | T. major (NT WA QLD) | |
| 9. | Lower glume distinctly rugulose | T. brassii (NT QLD) |
| Lower glume longitudinally ribbed | T. rubra (NT) |
Key to Thaumastochloa derived from de Koning, Sosef and Veldkamp
1983; Simon 1989b
Taxonomic name: