Rule 34 Dev - 2016 4_toes anal anal_sex animal_genitalia animal_penis anthro canine canine_penis casey_(artist) closed_eyes duo equine erection fur furry hair horse interspecies legs_up lying male mammal missionary_position moan monochrome nipples nude on_back open_mouth penetration penis precum precum_string sepia sex side_view toes yaoi|2356927368