| Name | Children | Media (from resource) | Traits |
|---|---|---|---|
| Xylariaceae | 1 | 0 | 0 |
| Xylariales | 1 | 0 | 0 |
| Xylochotridens | 1 | 0 | 0 |
| Xylochotridens rangifer | 0 | 0 | 1 |
| Xymenopsis Powell 1951 | 3 | 0 | 0 |
| Xymenopsis corrugata (Reeve 1848) | 0 | 0 | 2 |
| Xymenopsis corrugata (Reeve 1848) | 0 | 0 | 2 |
| Xymenopsis falklandicus Strebel (1908) | 0 | 0 | 1 |
| Yezoites | 1 | 0 | 0 |
| Yezoites bladenensis (Schlüter 1871) | 0 | 0 | 1 |
| Yoldia Møller 1842 | 3 | 0 | 0 |
| Yoldia eightsi | 0 | 0 | 1 |
| Aequiyoldia eightsii (Jay 1839) | 0 | 0 | 2 |
| Yoldia peninsularis | 0 | 0 | 1 |
| Aequiyoldia eightsii (Jay 1839) | 0 | 0 | 2 |
