In zoological anatomy, a cloaca's the posterior opening that serves as the only such opening for the intestinal and urinary tracts of certain animal species. The word comes from Latin, and means sewer. All birds, reptiles, and amphibians possess this orifice, from which they excrete both urine and feces, unlike placental mammals, which possess two separate orifices for evacuation. Marsupials and monotremes also possess one (in marsupials and a few birds, the genital tract's separate). In contra… (More on Cloaca)