Rule 34 Dev - animal_genitalia animal_penis anthro balls duo equine_genitalia equine_penis genitals grey_background horn male male/male muscular muscular_male penetration penile penile_penetration penis penis_in_penis simple_background urethral urethral_bulge urethral_penetration necrothant bovid bovine cattle equid equine horse mammal|17920493115