rule 34 2021 all fours anal anal knotting anal sex anal tugging animal genitalia animal penis anthro anthro on anthro anthro penetrated anthro penetrating anthro penetrating anthro anus ass ass up backsack ball size difference balls big balls big dom small sub big knot big muscles big penis blush canid canine canine penis canis claws domestic dominant duo ear piercing ear ring erection fur genitals hair intraspecies kihu knot knot root knotting looking pleasured male malemale male penetrated male penetrating male penetrating male mammal muscular muscular anthro muscular male narrowed eyes no internal organs nude open mouth open smile pawpads penetration penis penis size difference perineum piercing sex simple background size difference smile stomach bulge tongue tongue out were werecanid werecanine werewolf white background wolf 5108051