FusionDex.org

Parawak often hide in barren wastelands, planting their spores onto the bones of deceased Pokémon. Do not attempt to grab any bones you find in these wastelands, as they're usually infested with these poisonous spores.

A Parawak is the evolved form of a Cubone that has grown tough by overcoming the grief of losing its mother. Parawak are known to infest the roots of large trees en masse and drain nutrients.