Kingdom = animalia
Pylum = chordata
class = mammalia
Modern mammals are divided into three sub-classes:
Prototheria (Mammals that lay eggs, also known as monotremes or Monotremata).
Metatheria (marsupials, pouched mammals).
Eutheria (placental mammals. That's me).
Mammals are endothermic, have hair, a four-chambered heart, an single lower jaw, suckle their young, and are heterodonts. Not all mammals bear live young. Go read that bit about the Prototheria again.