| Name | Children | Media (from resource) | Traits |
|---|---|---|---|
| Abacionidae | 0 | 0 | 12 |
| Abacioninae | 0 | 0 | 2 |
| Aberrantidae | 0 | 0 | 10 |
| Ablechroiulidae | 0 | 0 | 12 |
| Ablechroiulinae | 0 | 0 | 2 |
| Abrocomidae | 0 | 0 | 12 |
| Abrsidae | 0 | 0 | 12 |
| Abylidae L. Agassiz 1862 | 0 | 0 | 12 |
| Abyssoanthidae Reimer & Fujiwara ex Reimer, Sinniger, Fujiwara, Hirano & Maruyama 2007 | 0 | 0 | 12 |
| Abyssochitonidae Dell' Angelo & Palazzi 1989 | 0 | 0 | 12 |
| Abyssochrysidae | 0 | 0 | 12 |
| Cottidae | 0 | 0 | 48 |
| Acalyptonotidae | 0 | 0 | 12 |
| Acanaloniidae | 0 | 0 | 12 |
| Acanthaceae | 0 | 0 | 12 |
