That's among the rextelum spawn, isn't it? Nowhere near the regular migration locations.
I was not sure if it still existed, but a random Eomon has been spawning in that area for years... probably after a large (10k - 20k) number of rextelum kills in the area.
Was confirmed to just be the eomon spawned by the rext.
I found 2 about 2 years ago, in that area. I kept going back to see if there are more, but never found. I'd like to know how they spawn...