The Artifact of the Gatekeeper is on this map, despite a number of discussions/comments to the contrary. It is located at: 49.1, 38.4, at the Centurion mini-boss, on top of the mountain, in the center of the arena.

You can lure the Centurion away, over the cliff edge, then just grab the artifact if you don't want to fight it (it does 1000-2000 damage per bite if your dino only has primitive saddle so be careful).