Finding this animal can be extremely difficult especially on official servers if you don't have a flyer yet. It's less rare near mountains and metal spawns. One of the most easy places to find one on the Island, is in the middle of redwood.
There’s a big open area near green obelisk, redwoods and swamp. If you are lucky you’ll find one. Beware though, spinos, rexes, raptors, carnos, barys, and theris are all relatively common around here. I’d recommend a good flyer or bruiser of your own if venturing here. Flak also helps.
You can find them in the redwoods, by obsidian mountain, and north of the beaver spawn near hunter cave. I highly advise using an Argentavis so you can just pick it up and knock it out in a safer spot.