This Aion quest can take forever if you dont know where to look. So here is the Ancient Lobnite Fossil quest guide:

1.Talk with Spiros in Verteron.
2.Find the Ancient Lobnite Fossil along the cliffs near the Citadel.
3.Bring the Fossil to Spiros for reward (3500XP + 700 kinah).

The fossil is just above the second mushroom up near the path to Tolbas Forest. This is where I found it. Face the path to Tolbas Forest, on the right there is a cliff with some mushrooms on it.

Location for Ancient Lobnite Fossil quest: