You see a fungosaurus
- Rraaaaa!
- CHEHEHE!!!
Notes
They can appear if a Primal Pod is not dealt with in time, or during the fight against The Primal Menace if a Primal Pack Beast is not killed in 20 seconds after spawning. A Fungosaurus will despawn if it is not killed within 5 minutes of spawning.
Abilities
Can deal Critical Hits
can cause feared status
can cause rooted statusDamage Taken From Elements
Physical 
Death
Holy
Ice
Fire
Energy
Earth
Location
Possibly at Sparkling Pools, Crystal Enigma and Monster Graveyard.
Strategy
If they appear during the hunt you should deal with them as you would with the other creatures, just being extra careful with its Root and Fear spells. During the fight against The Primal Menace, they should not be a priority, since you will have to keep killing other Primal Pack Beasts in order to continue the fight.