The Phanerozoic is the current geologic eon covers 541 million years ago to the present and is characterized by rapid emergence of a number of animal phyla the evolution of these phyla into diverse forms the emergence and development of complex plants the evolution of fish the emergence of insects and tetrapods and the development of modern faunas During this time span tectonic forces caused the continents to move and eventually collect into a single landmass known as Pangaea which then separated into the current continental landmasses