Is there a taxon that "adaptively" radiates faster?
The species from your list have some common traits:


Fast metabolism of themselves, food and fertilizers
sexual reproduction is more complex than crabs and coral
complex ecosystems and fast changing ecology 
lots of ecological competition generally advanced compared to ferns, moss and crabs 
More Possibility to travel through gene bottlenecks
recent in fossil history
prevalently small
possibility of population explosions
generalist and robust flexible habits and traits like tree nests, live birthing, flying, fangs, close inter-animal relations i.e. with bees,


If you study animals that have sedate speciation habits like platipus, they are limited in many of the common traits from that list. 

The animal is therefore mostly dependent on it's ecosystem's stability, richness and opportunities, as well as the specie's own physical wealth, opportunism and stability. Those species have very complex and flexible ecology cycles working over them at a high rate. The rate of change of the ecology is also dictated by the other's organisms ability to radiate in record times, so today's species are in an arms race of the fastest rates of change in predator-prey-reproduction traits, with all the tools of the trade, i.e. fast movement, strong protection, freaky efficient cell-type mutations, locomotive, feeding, protective and spacial habits that by themselves can define the base of the most prevalent recent families.

Some species RNA is more susceptible to change and has to be be counterbalanced with different checks, it's to keep up with the arms race of competition in the complex ecology spaces of most of the planet.