| Name | Children | Media (from resource) | Traits |
|---|---|---|---|
| Achaeus cranchii Leach 1817 (Cranch's spider crab) | 0 | 0 | 1 |
| Achaeus gracilis (O. G. Costa 1839) | 0 | 0 | 1 |
| Achelia | 2 | 0 | 0 |
| Achelia echinata Hodge 1864 | 0 | 0 | 1 |
| Achelia vulgaris (Costa 1861) | 0 | 0 | 1 |
| Achnanthaceae | 1 | 0 | 0 |
| Achnanthales | 2 | 0 | 0 |
| Achnanthes Bory de Saint-Vincent 1822 | 1 | 0 | 0 |
| Achnanthes longipes C. Agardh 1824 | 0 | 0 | 1 |
| Acidostoma Lilljeborg 1865 | 1 | 0 | 0 |
| Acidostoma obesum (Spence Bate 1862) | 0 | 0 | 1 |
| Aclididae | 1 | 0 | 0 |
| Aclis Lovén 1846 | 1 | 0 | 0 |
| Aclis attenuans Jeffreys 1883 | 0 | 0 | 1 |
| Acoetidae | 3 | 0 | 0 |
