- Xylonagra
- Xylonagra sp
- Xyloolaena type
- Xylopia discreta
- Xylosma
- Xyris sp
- Yahsimanisporites
- Yahsimanisporites batillatus
- Yahsimanisporites bransonii
- Yahsimanisporites subbransonii
- Yahsimanisporites subyahsimani
- Yahsimanisporites trivalvis
- Yahsimanisporites yahsimani
- Yalisphaeridium
- Yalisphaeridium baculatum