They are part of the jungle spawn pool. To find go to either : south east coast up to green ob, also south and east of the foot of the volcano. West coast from red ob up to the river (not on beach, inland). If you see Rex or ankylo you are in the greenland biome. Wiki is full of shit, while they do indeed spawn in the redwood, the spawners there are set to 13 Dino's instead of the regular 23 a regular spawner would have.
They are on the rarer side of the spawn pool just a tiny bit less of them than carnos.
I have found that they are EXTREMELY common at Cragg’s Island, which is the bottom southwest island at The Island, near the main river running through it. I have found more than one ever time I go there. Look for the small clearing on the right side of the river near the bottom of the island. There is also many easy tame animals there.
Can be found on scorched earth around red ark, to tame easy, use full gilli suit, bola fly around mountains until u see high lvl to tame, kill everything around it, making sure u don't spoil it, wait till it lands and make your advances, don't land too close or your mount will spoon it. Get bola ready, take aim and shoot. Shooting in the head will take down this tame nearly instantly