If you can't find these guys easily, I recommend using a Snow Owl. Flying high in the redwood, and with the Owl vision you can spot every creature in there from far away. If you don't have the Extinction DLC to tame Owls, just buy one from a player of your server, or use a command to spawn them.
Easiest way to tame: make a dino pen, pick one up with an argy, put it in the dino pen then follow along with a basic taming process (knock it out, feed it). Make sure you have lots of narcotics on you!
Best thing about them: they can climb up really steep hills and they can potentially do lots of damage and can be fast.
Where to find: most commonly found on trees (they will be hanging upside down, high up on large trees) in the redwood forest areas (mainly on The Center) or I find lots of them in the Ragnorok desert.