The same goes for everything that lives then. There is no such thing as a mammal, they are just a form of prototheria! A lot of them just evolved into what we consider marsupials or eutheria. But a koala is just as much a mammal as a lemur!

Now this is a much smaller branch ofc, but you could slap it onto anything more vague. Reptiles, fish, crabs… and worse… fungi. Not to mention the archea.