Just a really big stego under steroids...

Actually, the stego is a kind of better than this big dude, BC considering the number of bushes they'd farm, the amount of berries is much higher with stego

Plus the fact that the stego is faster, and has lower turn radius

Last point, when you're traveling around, due to the fact the bronto is much larger than his little bro, he'd glitches much more often