No.
The finches on Galapagos Islands. Marsupials provide another example.
Adaptive Radiation :)
Adaptive radiation is the term for biodiversity that results from few ancestral species.
An adaptive zone is an environment which allows the development of adaptive radiation.
Divergent evolution is also known as adaptive radiation.
Adaptive Radiation is likely to produce a cluster of species in a short period of time.
Adaptive radiation spread them into many land niches
adaptive radiation formed mant new land plant species
adaptive radiation
Adaptive Radiation
It's been long isolated, so species found niches there which weren't coveted by more adaptive animals. Even so, the monotremes (echidnas and platypuses) are just hanging on and some marsupials, notably the thylacine, have lost out to their placental counterparts (in that case, the dog).
Darwin's finches are a great example of adaptive radiation, where a common ancestor species diversifies into multiple species to exploit different ecological niches. This process of adaptive radiation is a key mechanism in evolutionary biology to explain the diversity of life forms.