Eutheria, mammals that carry their young in the womb until fully developed, are the most familiar of the mammalian groups - a fact that is not surprising, since this is the group to which humans belong. Spec's eutherians are much less diverse than those of our home timeline, although even in Spec, the "true beasts" make up more than two thirds of the planet's mammalian species. Some eutherians, such as the xenarthrans and primates, are present in both Spec and RL, while others, such as the paraselenodonts, are endemic to this timeline.