Kingdom = Animalia
Phylum = Chordata
Subphylum = Vertebrata
Class = Mammalia
Subclass = Prototheria
All living prototheria are of the
Order Monotremata
Also known as Monotremes, these are egg-laying Mammals. After hatching, the young are carried in their parents' pouches. The monotremes live only in Australia and New Guinea. The only living Genera are Ornithorhynchus (the Platypus or Duckbilled Platypus) and Tachyglossus (the Spiny Anteater or Echidna).
Dragoon has informed me that monotemes use the same opening for urine and faeces.
And if we're going to add on interestering facts, it is also worth noting that monotremes loose their teeth at adulthood. (in platypuses they are replaced by 'horny pads').