One turnover I like is when he turtles, you go to the side and keep your weight on him( say his rite).wWth your rite arm, reach under his armpit and grab his wrist. Keeping your weight on him, drive your forearm into his tricep, hard. If done properly this should cause him some pain and his hips will rise slightly and forward to ease it. Keeping your weight on his front rite quarter and driving down hard still with the forearm reach around under his crotch with your left. Grab his crotch hard and lift him over his front rite quarter keeping him close to you tite. Don't let go of his arm. Keep it in tite to you. It's yours. As he rolls over, ride or drive your body up his. You have to keep stuck to him. there you will have side control and his arm in your control for easy sub. If you don't keep him tite, at least you turned him and can face off again.
IMO, the turtle is a very, very underrated position in mma. It is far better than being mounted and there are too many mounts happening. A good judoka is excellent at defending in turtle position and in mma they wont give the bjjer 6 min to get thru. Havent seen the turtle get smoked in mma yet and have actually seen it as a decent last resort defense. Nak used it well vs Vov.