Meanings of oviparous monotremes in English

The marsupials, a second sub-class, come next to the oviparous monotremes, the oldest of the mammals.

This is the case also with the lowest mammals, the oviparous Monotremes and most of the Marsupials.

It is then clear that the Marsupials-viviparousMammals without placenta-are a necessary transition from the oviparous Monotremes to the higher Placentals with chorion-villi.