| Name | Children | Media (from resource) | Traits |
|---|---|---|---|
| Xanthorrhoeaceae | 1 | 0 | 0 |
| Xenosyllis Marion & Bobretzky 1875 | 1 | 0 | 0 |
| Xenosyllis scabra (Ehlers 1864) | 0 | 0 | 1 |
| Xerohippus | 1 | 0 | 0 |
| Xerohippus azami (Bolívar & I. 1901) | 0 | 0 | 1 |
| Xya | 1 | 0 | 0 |
| Xya pfaendleri Harz 1970 | 0 | 0 | 1 |
| Xystodesmidae | 1 | 0 | 0 |
| Yoldia Møller 1842 | 3 | 0 | 0 |
| Yoldia laevigata | 0 | 0 | 1 |
| Yoldia lata (Hinds 1843) | 0 | 0 | 0 |
| Yoldia nitida | 0 | 0 | 0 |
| Yoldiidae Dall 1908 | 1 | 0 | 0 |
| Zerynthia | 1 | 0 | 0 |
| Zerynthia cerisy (Godart (1824)) | 0 | 0 | 1 |
