Surviving groups of bristle worms flourish in the underground watery labyrinths beneath the Central Desert, 200 Million AD. Several species live below the Central Desert and they are all descended from a single ancestor, a marine trichobranchid bristle worm that thrived in this region when it was covered by shallow seas. When sea levels dropped, the worms were trapped, but they survived and adapted to their new environment, slowly evolving to fill the different niches the cave system offered. This process is called adaptive radiation.