| Name | Children | Media (from resource) | Traits |
|---|---|---|---|
| Aporrhaididae | 0 | 0 | 0 |
| Aporrhais da Costa 1778 | 1 | 0 | 0 |
| Aporrhais serresianus | 0 | 0 | 1 |
| Arca Linnaeus 1758 (Ark clam) | 1 | 0 | 0 |
| Arca noae Linnaeus 1758 (Noah's arch) | 0 | 0 | 1 |
| Archaeogastropoda | 3 | 0 | 0 |
| Arcidae Lamarck 1809 | 2 | 0 | 0 |
| Arcoida | 2 | 0 | 0 |
| Ardeidae (herons and bitterns) | 2 | 0 | 0 |
| Arthropoda (arthropods) | 4 | 0 | 0 |
| Ascomycota (sac fungi) | 1 | 0 | 0 |
| Atherina (friars) | 1 | 0 | 0 |
| Atherina hepsetus Linnaeus 1758 (Mediterranean sand smelt) | 0 | 0 | 1 |
| Atherinidae (Old World silversides) | 1 | 0 | 0 |
| Atheriniformes | 1 | 0 | 0 |
