Cloaca

The cloaca is a common rear opening in land vertebrates. Through this opening, the animals expel urine and faeces, and carry out reproduction.

The cloaca is a primitive or 'basal' feature of tetrapods. All amphibia, all sauropsids (reptiles and birds) and even monotreme mammals have a cloaca.

A different method is used by therian mammals, such as marsupials and placentals. They have an anus for defecation, and another opening for urine and sexual reproduction.

This short article about biology can be made longer. You can help Wikipedia by adding to it.