This is how I got a high lvl equus:

I was just looking for a high lvl baryonx on the back of my argy and I found a group of equus one of them was a lvl 145 (max 150) suddenly a Rex started to attack them ,startled all of them started running randomly, but the lvl 145 started running in the water ,then a sarco started to chew on it's ass i swooned down and grabbed the lvl 145 equus and put it in a taming pen near my base.

I named it "The Lucky One" cuz' if I wouldn't have been there in my argy he would be in the sarcos belly. BTW I tamed it using a 10x balm