Eutheria

He knows a lot about the science stuff, Professor Dave Explains About 95% of all extant mammals are placental mammals.

These are part of subclass Theria, which includes the marsupials, and infraclass Eutheria, whose name actually comes from Greek and roughly translates to good beast.

So you can see that we're a bit biased when it comes to naming certain taxa.

Another term for Eutheria is Placentalia, which includes only the placental mammals, which are partly distinguished from monotremes, or egg-laying mammals, and marsupials, or pouched mammals, in that the fetus is carried in the uterus of its mother to a relatively late stage of development, much later than the marsupials, who although they do nourish their young via a placenta, give birth to less developed young that are further nurtured within the mother's pouch.

This is the grouping we will be using to explore the diversity of the placental mammals, as backed by molecular data from 2022.

However, this is by no means the only proposed grouping of the placental mammals.

But for now, let's focus on 19 proposed orders.

Most modern analyses place these orders into the primary lineages of Afrotheria, Xenarthra, Euarchontoglires, or Supraprimates, and Laurasiatheria, which are further broken down into subgroupings and orders.