You can't tame these guys by knocking them out. Instead, you need to steal their fertilised eggs (just like wyverns and rock drakes), hatch them and raise them, just a bit harder than knocking them out. The eggs can, of course, be found in their nests and do be careful while trying to steal one as the Deinonychus is very territorial. Hope this helps :)
Here's how to steal one early game: If you spawn in at chalk hills 3 and spawn next to a pond walk opposite to the pond. There are some nests right there. Snatch one quickly and run off the cliff next to the pond. Be careful and make sure to fall into the water. From there make a left and you should get to a beach area. From there it should be easy to find your base.
1. Tame a kangaroos 2. Have a tribe mate with a whip in the pouch 3. Quickly jump on a nest and have your tribe mate whip the egg into his inventory 4. Jump away! No one has to dismount so there’s basically no risk
Just wait until they get distracted (they usually will) or lure them to another dino. Once they are distracted fly in, and make sure you land the bird close to you and snatch the eggs and fly off. You can then check what level it is while high up. :)
If you are alone, ride a pteranodon. This is because they cannot latch onto a pteranodon, but they can latch onto an argentavis. Lead the deinonychuses away from the nest and into a group of brontosauruses. Agro the brontos and make them hit the deinonychuses, and then watch carnage ensue. Rinse and repeat until the deinonychuses have all died, make sure brontos aren't agroed and then safely snatch the eggs from the nests. Using a whip is an optional choice to make things run smoother and faster. After this process, go somewhere else for a few minutes and come back to do it again. With very little practice, this can be a very effective method.
If there are no brontos in the area, use the pteranodon as a weapon. Swoop in and twirl into the deinonychuses until they die. WATCH OUT for raptors. They WILL dismount you in a heartbeat, whether they were targetting you beforehand or not. After the deinonychuses are dead, swoop in and snatch the eggs before leaving and repeating the process.
Deinonychus eggs can only be gotten like the rock Drake or wyverns, you just steal a fertilized egg from their nest. Normally I would use a snow owl to freeze it while my tribe mate grabs the eggs. Or you can have a gun and a dinosaur with good melee. (The gun to shoot it if it latches on your mount). And kill them and grab the eggs.
For all I know they are only found in the white cliffs in packs. There is a set of ruins with bridges. The nests that I know of are near the bridges guarded by rock elementals as well as the new fluffy raptor
This new guy is pretty much like a raptor. There are 4 imprints 8 hour apart from each other. The egg incubation is 5 hours (like a Wyv). The baby stage is roughly 4 hours and the baby will be a Juvy at 10% (like any normal baby). Be careful though if hatching low level guys as they eat 3 meat per sitting so they go through it fast, and if leaving overnight there is a chance of starvation. Mine was a 140 and it’s food value is 3800. We hatched them Sunday morning at 10:30am (Juvy by 2:30pm) and my final Imprint is Monday evening at 6:30. He is now an Adolecent. Saddles unlock at lvl 32. Hopefully this helps you all because we had to test it in order to get the proper information. (R.I.P Lvl 100). GoodLuck !