I searched half the map for these little guys but couldn't find them anywhere EXCEPT the large trench located in the jungle in the center of the map. (The trench may have spinos, sarcos, arthos, and tintana boas) If you enter the trench and can't find them try looking up river in the trench (near the waterfall and lake in the trench). If you go tho this trench I guarantee you will find them. Once you find them if you have chiton they are pretty easy to tame.